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Ourlast posting detailed how cruising at around displacement speed dramatically decreases fuel consumption and increases cruising range. It also highlighted the problems which can be encountered through cruising consistently at low rpm. Running diesel engines for long periods at idling speed is particularly detrimental and engine “wear” is said to occur at about double the ratecompared to running them under normal loading. Ideally for that reason engines should only have 3-5 minutes of idling followingstart up and then be brought up to around 1,200 rpm withsome load applied.

Not only can idling cause a build-up of carbon in the engine but also causes mirror glazing, which is the creation of a mirror-like surface finish on cylinder bores, eventually allowing more oil to pass the rings and creating more blow-by (the adverse effects of which were detailed in Part 1 of this article). Mirror glazing can also be caused by constantly running engines at the same rpm, so this should be avoided. Before shut down a diesel should also be idled for 3-5 minutes to allow the turbo to cool down. In practice this is catered for when entering your marina or approaching your anchorage.

Now let’s consider someoptions for low speed cruisingand their relative merits.

Option 1 – run both engines at low rpm

If you’re wanting to do this, avoid running below 1,200 rpm andit’s recommended to at least run at 60-75 per centof WOTfor about 30 minutes after reaching full operating temperature, then again for about15 minutes every 4 hours and then for about 30 minutes about 1 hour before shutdown. This last one is considered to be especially important to reduce soot formation and to clean the turbocharger andit’s better to spend less than optimal time at higher rpm than none at all.

Pros 

There will be a considerable reduction in fuel usage and increase in range.

All ancillary equipment driven by the engines such as power steering, refrigeration compressors, hot water manifolds will operate (unlike Option 2).

Both gearboxes and drive trains will be cooled (unlike Option 2).

Full maneuverability is maintained and there is no rudder bias (unlike Option 2).

There is no potential problem with prop shaft couplings (unlike Option 2).

In practical terms this option is easy to manage.

Cons 

Somemonitoring and planning is required for the periods at higher rpm and it is difficult to achieve on short cruises.

May cause issues with alternators.

Hours-based service costs may increase because you are using more engine hours to run a given distance.

Option 2 – run on one engine at a time at higher rpm

Underthis system only one engine is used at a time, alternatingperiodically(eg every one to two hours).

Pros 

It will take more rpm on the one selectedengine to reach your chosenspeed than it would be using two, therebyeliminatingor at least minimisingthe problem of light loading.

Fuel saving and range increase will be considerably less than Option 1, but still in the order of 10 to 15 per cent.

Higher rpm will make your in-use alternator run more efficiently.

The process is relatively east to manage.

The frequency of hours-based engine servicing is reduced thus saving service costs.

Cons 

Maneuverability is considerably reduced using one engine, particularly at low speedso this option should only be considered in open waters and not for example coming into or out of marinas.

There will be a slight steering bias in the direction away from the in-use engine ie using only the port engine the vessel will veer slightlytowardsstarboard.

The not-in-use engine’s prop will still turn or “windmill” causing drag and the gearbox to operate.The inactive engine’s gearboxmust be kept in neutral so that the engine doesn’t turn over. Most gearboxes are water-cooled using its engine’s heat exchanger, so without the engine running this cooling will be lost and gearbox damage can potentially occur. Consult your installations Owners’ Manual to ascertain for how long you can windmill. They normally suggest running your engine for about five minutes before wind milling and will advise the allowed time interval before it needs to be started again to activate the heat exchanger and circulate gearbox oil. My Caterpillar manual recommends idlingthe engine every 12 hours for five minutes, however the Twin Disc gearbox manual recommends idling the engine for a few minutes every hour, so I willfollow that guideline.

If initiating this procedure it would be a good idea to check the temperature atthe rear of the wind milling prop’s gearbox using an infra-red thermometer to see how long it takes for the temperature to rise. The lower the boat speed, the less the wind milling engine’s gearbox temperature will rise. Bear in mind there’s a good chance that some time in the future you’ll have a problem with one engine and need to run just on the other one, so this is not a wasted exercise.

Take into account that engines often run ancillary equipment, for example Rapport’s port engine runs our refrigeration compressor while her starboard engine runs our power steering and heats our hot water supply.

Some stuffing boxes have no cooling system beyond the sea water coming into it, others have oil or grease lubrication to keep temperatures down, while others and more particularly most dripless shaft seals are cooled with sea water supplied from the engine’s sea water pump, so for this latter category no cooling will be supplied if the engine is not running.

Note that some vessels have a system where either engine can supply cooling water to both shafts. However if this is not the case it is best to comparethe temperaturesof the not-in-use shaft seals with the in-use shaft seals using an infra red thermometer to determine for how long you can allow wind milling. A temperature up to about 40dC should be OK, in fact as a general rule mechanics say if the stuffing box is nottoo hot to touch it’s OK (be careful doing this though). Another measure is that stuffing box temperature should be 7-22dC above sea water temperature.

Note that some cruisers have adopted measures to eliminate wind milling. At an extreme level one cruiser crossing the Pacific decided to remove oneprop until half way across, then replacethe prop and removethe other one so the in-use engine could be changed. This was done at sea using a block and tackle to support the prop’s weight. At a less extreme level it’s not uncommon for long distance cruisers to install a mechanical or hydraulic system enabling either prop shaft to be locked so it cannot rotate. I have discounted the use of such a system based on the inconvenience and practicalityof changing over engines and the compromise to maneuverability in the event of an emergency.

When an engine is driving your vessel it is trying to push the prop shaft and coupling flangetowards the engine, therefore not putting any load on the securing bolts. When the prop shaft’s wind milling it’strying to pull away fromthe engine and therefore your coupling flange, soconnections should be checked initially and at regular intervals thereafter.

Option 3 – run both engines with one engine at higher rpm than the other

Another option isto run one engine at high rpm and the other at low rpmso that all engine-driven equipment is operating, then interchange every couple of hours or so. If adopting this option avoid running the low rpm engine below1,200 rpm for the reasons outlined in the opening comments.

Pros 

The issue of light loading is eliminated.

Economy gains similar to running two engines at low rpm are achieved and range is increased.

There is littleloss of maneuverability.

There is no issue with cooling of gearboxes and shaft seals.

There is no issue with prop shaft flange connections.

The process is easy to manage.

All engine-driven ancillary equipment will operate.

Cons 

Both engines are stillrampingup engine hours, so no servicing costs are saved.

There will be a very slight steering bias in the direction away from engine operating at higher rpm.

The alternator’s efficiency is compromised for the engine running at low rpm.

Conclusion

As mentioned early on Di and I prefer to cruise much of the time off the plane, even when cruising long distances,so considering all of the above options here’s a practical solution based on Option 2 for Rapport.

-Start both engines and leave the marina using bothat low rpm (although preferably above 1,200 rpm wherever possible)providingmaximum maneuverability.

-When in openwatersshut down the starboard engine and as temperatures rise, gradually increase rpm on port to about 1,850 = 66 per cent of WOT. This will operate refrigeration and efficient alternator operation and battery charging at higher rpm. The power steering willnot operateso hand steering will be necessary, however this is not much of an issue in open waters. Any time that power steering and autopilot is wanted I can start the starboard engine.

-When the freezer reaches its operating temperature (after roughly three hours on first day outand on subsequent daysafter about an hour), runthe starboard engine at about 1,850 rpm and shut down port

–Then continue to alternate engines as required about hourly.

For subsequent days wenormally use the genset every morning so the batteries are fully charged at that time and the alternators don’t need to run at high outputs. Every several engine hours I’ll run both engines at about 2,200-2,400rpm for 15 minutes or so as well as doing this for about half an hour an hour before shutdown.

Happy Slow Cruising

Ourlast posting detailed how cruising at around displacement speed dramatically decreases fuel consumption and increases cruising range. It also highlighted the problems which can be encountered through cruising consistently at low rpm. Running diesel engines for long periods at idling speed is particularly detrimental and engine “wear” is said to occur at about double the ratecompared to running them under normal loading. Ideally for that reason engines should only have 3-5 minutes of idling followingstart up and then be brought up to around 1,200 rpm withsome load applied.

Not only can idling cause a build-up of carbon in the engine but also causes mirror glazing, which is the creation of a mirror-like surface finish on cylinder bores, eventually allowing more oil to pass the rings and creating more blow-by (the adverse effects of which were detailed in Part 1 of this article). Mirror glazing can also be caused by constantly running engines at the same rpm, so this should be avoided. Before shut down a diesel should also be idled for 3-5 minutes to allow the turbo to cool down. In practice this is catered for when entering your marina or approaching your anchorage.

Now let’s consider someoptions for low speed cruisingand their relative merits.

Option 1 – run both engines at low rpm

If you’re wanting to do this, avoid running below 1,200 rpm andit’s recommended to at least run at 60-75 per centof WOTfor about 30 minutes after reaching full operating temperature, then again for about15 minutes every 4 hours and then for about 30 minutes about 1 hour before shutdown. This last one is considered to be especially important to reduce soot formation and to clean the turbocharger andit’s better to spend less than optimal time at higher rpm than none at all.

Pros 

There will be a considerable reduction in fuel usage and increase in range.

All ancillary equipment driven by the engines such as power steering, refrigeration compressors, hot water manifolds will operate (unlike Option 2).

Both gearboxes and drive trains will be cooled (unlike Option 2).

Full maneuverability is maintained and there is no rudder bias (unlike Option 2).

There is no potential problem with prop shaft couplings (unlike Option 2).

In practical terms this option is easy to manage.

Cons 

Somemonitoring and planning is required for the periods at higher rpm and it is difficult to achieve on short cruises.

May cause issues with alternators.

Hours-based service costs may increase because you are using more engine hours to run a given distance.

Option 2 – run on one engine at a time at higher rpm

Underthis system only one engine is used at a time, alternatingperiodically(eg every one to two hours).

Pros 

It will take more rpm on the one selectedengine to reach your chosenspeed than it would be using two, therebyeliminatingor at least minimisingthe problem of light loading.

Fuel saving and range increase will be considerably less than Option 1, but still in the order of 10 to 15 per cent.

Higher rpm will make your in-use alternator run more efficiently.

The process is relatively east to manage.

The frequency of hours-based engine servicing is reduced thus saving service costs.

Cons 

Maneuverability is considerably reduced using one engine, particularly at low speedso this option should only be considered in open waters and not for example coming into or out of marinas.

There will be a slight steering bias in the direction away from the in-use engine ie using only the port engine the vessel will veer slightlytowardsstarboard.

The not-in-use engine’s prop will still turn or “windmill” causing drag and the gearbox to operate.The inactive engine’s gearboxmust be kept in neutral so that the engine doesn’t turn over. Most gearboxes are water-cooled using its engine’s heat exchanger, so without the engine running this cooling will be lost and gearbox damage can potentially occur. Consult your installations Owners’ Manual to ascertain for how long you can windmill. They normally suggest running your engine for about five minutes before wind milling and will advise the allowed time interval before it needs to be started again to activate the heat exchanger and circulate gearbox oil. My Caterpillar manual recommends idlingthe engine every 12 hours for five minutes, however the Twin Disc gearbox manual recommends idling the engine for a few minutes every hour, so I willfollow that guideline.

If initiating this procedure it would be a good idea to check the temperature atthe rear of the wind milling prop’s gearbox using an infra-red thermometer to see how long it takes for the temperature to rise. The lower the boat speed, the less the wind milling engine’s gearbox temperature will rise. Bear in mind there’s a good chance that some time in the future you’ll have a problem with one engine and need to run just on the other one, so this is not a wasted exercise.

Take into account that engines often run ancillary equipment, for example Rapport’s port engine runs our refrigeration compressor while her starboard engine runs our power steering and heats our hot water supply.

Some stuffing boxes have no cooling system beyond the sea water coming into it, others have oil or grease lubrication to keep temperatures down, while others and more particularly most dripless shaft seals are cooled with sea water supplied from the engine’s sea water pump, so for this latter category no cooling will be supplied if the engine is not running.

Note that some vessels have a system where either engine can supply cooling water to both shafts. However if this is not the case it is best to comparethe temperaturesof the not-in-use shaft seals with the in-use shaft seals using an infra red thermometer to determine for how long you can allow wind milling. A temperature up to about 40dC should be OK, in fact as a general rule mechanics say if the stuffing box is nottoo hot to touch it’s OK (be careful doing this though). Another measure is that stuffing box temperature should be 7-22dC above sea water temperature.

Note that some cruisers have adopted measures to eliminate wind milling. At an extreme level one cruiser crossing the Pacific decided to remove oneprop until half way across, then replacethe prop and removethe other one so the in-use engine could be changed. This was done at sea using a block and tackle to support the prop’s weight. At a less extreme level it’s not uncommon for long distance cruisers to install a mechanical or hydraulic system enabling either prop shaft to be locked so it cannot rotate. I have discounted the use of such a system based on the inconvenience and practicalityof changing over engines and the compromise to maneuverability in the event of an emergency.

When an engine is driving your vessel it is trying to push the prop shaft and coupling flangetowards the engine, therefore not putting any load on the securing bolts. When the prop shaft’s wind milling it’strying to pull away fromthe engine and therefore your coupling flange, soconnections should be checked initially and at regular intervals thereafter.

Option 3 – run both engines with one engine at higher rpm than the other

Another option isto run one engine at high rpm and the other at low rpmso that all engine-driven equipment is operating, then interchange every couple of hours or so. If adopting this option avoid running the low rpm engine below1,200 rpm for the reasons outlined in the opening comments.

Pros 

The issue of light loading is eliminated.

Economy gains similar to running two engines at low rpm are achieved and range is increased.

There is littleloss of maneuverability.

There is no issue with cooling of gearboxes and shaft seals.

There is no issue with prop shaft flange connections.

The process is easy to manage.

All engine-driven ancillary equipment will operate.

Cons 

Both engines are stillrampingup engine hours, so no servicing costs are saved.

There will be a very slight steering bias in the direction away from engine operating at higher rpm.

The alternator’s efficiency is compromised for the engine running at low rpm.

Conclusion

As mentioned early on Di and I prefer to cruise much of the time off the plane, even when cruising long distances,so considering all of the above options here’s a practical solution based on Option 2 for Rapport.

-Start both engines and leave the marina using bothat low rpm (although preferably above 1,200 rpm wherever possible)providingmaximum maneuverability.

-When in openwatersshut down the starboard engine and as temperatures rise, gradually increase rpm on port to about 1,850 = 66 per cent of WOT. This will operate refrigeration and efficient alternator operation and battery charging at higher rpm. The power steering willnot operateso hand steering will be necessary, however this is not much of an issue in open waters. Any time that power steering and autopilot is wanted I can start the starboard engine.

-When the freezer reaches its operating temperature (after roughly three hours on first day outand on subsequent daysafter about an hour), runthe starboard engine at about 1,850 rpm and shut down port

–Then continue to alternate engines as required about hourly.

For subsequent days wenormally use the genset every morning so the batteries are fully charged at that time and the alternators don’t need to run at high outputs. Every several engine hours I’ll run both engines at about 2,200-2,400rpm for 15 minutes or so as well as doing this for about half an hour an hour before shutdown.

Happy Slow Cruising

 Although fiveof the six boats we’ve owned since the 1980s have been planing boatsa large chunk of ourcruising has been in the Med aboard Envoy at around 6 knots. During that time we really grew to enjoy life in the slow lane and now find that even though our current boat, Rapport, is capable of about 20 knots we prefer to cruise mostly around 8-10 knots.

Most our time aboard Envoy we cruised at about 6kn. Max speed was about 8kn

Most cruisers we speak to own twin-engine planing vessels and many of these choose to cruise on the plane when going some distance to their destination, but then cruise off the plane in the general area around their destination. There are some goodreasons for this philosophy including some of these:

– You’re on the water torelax so why not enjoy the journey as well as the destination

– Helming at slower speed needs less attention so you can leisurely enjoy the scenery at your leisure and have more time to navigate safely, especiallyin what may be an unfamiliar area

– Many skippers prefer to tow their RHIBs at slower than planing speeds

– You’re often close to shore where in any case speed is limited to 5 knots (within 200 metres)

– At slower speeds you generally don’t have to movegear aroundas you often need to in all but calm conditions when going on the plane

– At slower speeds you’re not generating so much engine noise or causing so much wake

– Slower speeds aregenerally more comfortable for crew and it’s easier to undertake activities like making cups of coffee, using the head or having lunch under way

– At slower speeds your journey will take longer allowing more time for battery charging, for engine-driven compressors to reduceyour refrigeration temperatures and for manifold hot water heaters to heat up. This is important because if for example we leave our marina for Oneroa and cruise at planing speed after the engines are up to temperature the journey will take about 90 minutes and this is insufficient time for the refrigeration to becomefully effective. At 8 knots or so the cruise will take about three hours which allows plenty of time. This is not so much of an issue on the following days when refrigeration is already cold

– At slower speeds you can troll and catch a kahawai or kingi on the way (good luck withthat one!)

– Due to lower rpm at slower speeds you’re saving a considerable amount in fuel costs and increasing your cruising range between fueling stops

In addition to these factors by nursing your engines along at low rpm you’re looking after them right? Actually NO – this is quite wrong so read on.

Although Rapport’s top speed is about 21kn fully-loaded, we prefer to cruise at 8-10kn

So let’s focus on reduced fuel consumption and increased rangeeven though weand most people we know aren’t greatlyconcerned about fuel costs, understanding this is one of the cheapest of boating costs.

Here are fourexamples of fuel savings and increases in range (taken from Pacific PowerBoat magazine boat reviews). Note that fuel usage expressed in litres per nm is more relevantthan litres per hr as the former takes into account the shorter distance traveled due to slower speeds.

1. Nimbus 405 13.3m LOA planing vesselwith twin 200hp Volvos and shaft drives:

At 3,000 rpm = 17kn, 95.9 litres/hr, 4.4 litres/nm, 200 nm range

At 1,000 rpm = 7.3kn, 6.5 litres/hr, 0.9 litres/nm, 1,000 nm range – sofuel usage per nm decreases and range increases by a factor of about 5x

2. Absolute Vavetta 14.9m LOA semi-displacementvessel with twin Volvo Penta IPS650 “Pods”, each 480hp:

At 3,000 rpm = 18.7kn, 112 litres/h, 6 litres/nm, 272 nm range

At 1,500 rpm = 7.3kn, 21 litres/hr, 2.9 litres/nm, 564 nm range

At 1,250 rpm = 6.1kn, 9 litres/hr, 1.4 litres/nm, 1,137 nm range – so fuel usage per nm decreases and range increases by a factor of about 4.2x

3. Maritimo S55 17m planing vessel with twin Volvo D13 each 400hp and shaft drives:

At 2,100 rpm = 23.8kn, 226 litres/hr, 9.5 litres/nm, 430 nm range

At 900 rpm = 8.1kn, 26litres/hr, 3.2litres/nm, 1,280nm range – so fuel usage per nm decreases and range also increases by a factor of about 3x

4. Circa 24 –26m LOAdisplacement vessel with twin Scania DI 090, each 250hp @ 1,800rpm and shaft drives:

At 1,500 rpm = 12.3kn, 39.2 litres/hr, 3.2 litres/nm, 3,234 nm range

At 1,000 rpm = 8.7kn, 13.3 litres/hr, 1.52 litres/nm, 6,809 nm range – so fuel usage per nm decreases and range increases by a factor of about 2.1x. Note that at 6.5kn the range increases to over 10,000nm

Theseexamples include displacement, semi-displacement and planing vessels and similar results apply to all standardvessels including single engine vessels and yachts under power(however I’m not sureif this applies with foils.)

The above resultsare based on running both engines and we can see that reducing rpm results in a substantial decrease in fuel consumed per nm combined with a substantialincrease in range as a result of cruising closerto the vessel’s displacement speed where the boat’s hull becomes wonderfully efficient. That’s why long distance cruisers are nearly always displacement vessels or faster vessels cruising at displacement speed. The figures would be even more impressive if I’d compared maximum rpm with idling rpm, but I wanted to compare realistic speeds.

Howeverthere are somedownsidestocruising at low rpm and I want to mentionthese as well as suggesting several alternative options to minimise their effects. These thoughts are based on our own experiences and some internet research as well as discussions with four diesel mechanics over the last several years.

Diesel engines are not designed to be run for long periods at light loading, which is defined as rpm less than 40 per cent of wide open throttle (WOT). On the contrary the suggestedrule of thumb is to run enginesat 60-75 per cent of WOT for 60-75 per centof the time,this 60-75 per centrange beingthe range of mechanics’ varying opinions.

So what happens if you do consistently run at light loading rpm?

At low rpm and therefore lower than optimum engine temperature the piston rings don’t seat so well resulting in faster wear, additional blow-by (more than double thenormal), oil fouling of components such as turbos and carbonisation.Blow-by is the phenomenon whereby combustion chamber gasses consisting of unburned fuel and water vapour as well assoot bypass the rings causing a harmful sludge to build up on the rings in the processand to enter the crankcase. Some blow-by is normal, but increased levels cancontaminate lubricating oil forming a sludge that can partially block lubrication feed lines as well asacids that attack engine parts,often resultingnot only in later engine problems but in significantly reduced engine life.

This is one of several reasons why engines used in commercial vessels generally have a longer life span than in pleasure vessels, that is theirengines are mostly selected according to their intended operationalspeed and therefore rpm.

Another cause of increased blow-by is over filling lubrication oil so never add oil beyond the dipstick marking.

Additionally alternators don’t operatesowell at low rpm. For example aboard Rapport which has24V battery banksour approx 50amp alternators charge at 23 amps at 1,170rpm and 36 amps at 1,510rpm – a 57 per cent difference. At low engine rpm alternators’ cooling fansalso run more slowly causing alternators to overheatparticularly in the early stages of charging when the battery banks need for charging is greatest and the alternators are working their hardest. Leaving the marina this should not be too much of a problem as most vessels have shore powered chargers.

A negative for running slower is it results in more engine hours accumulating for the same distance cruised theoreticallyresulting in an increase in service costs, though practically many vessels have an annual service without reaching their hours of service threshold.

But don’t despair as there are several options available to run vessels at lower speeds without compromising engine wear or longevity, each option having its own pros and cons. 

Read about these options in our next posting.

 Although fiveof the six boats we’ve owned since the 1980s have been planing boatsa large chunk of ourcruising has been in the Med aboard Envoy at around 6 knots. During that time we really grew to enjoy life in the slow lane and now find that even though our current boat, Rapport, is capable of about 20 knots we prefer to cruise mostly around 8-10 knots.

Most our time aboard Envoy we cruised at about 6kn. Max speed was about 8kn

Most cruisers we speak to own twin-engine planing vessels and many of these choose to cruise on the plane when going some distance to their destination, but then cruise off the plane in the general area around their destination. There are some goodreasons for this philosophy including some of these:

– You’re on the water torelax so why not enjoy the journey as well as the destination

– Helming at slower speed needs less attention so you can leisurely enjoy the scenery at your leisure and have more time to navigate safely, especiallyin what may be an unfamiliar area

– Many skippers prefer to tow their RHIBs at slower than planing speeds

– You’re often close to shore where in any case speed is limited to 5 knots (within 200 metres)

– At slower speeds you generally don’t have to movegear aroundas you often need to in all but calm conditions when going on the plane

– At slower speeds you’re not generating so much engine noise or causing so much wake

– Slower speeds aregenerally more comfortable for crew and it’s easier to undertake activities like making cups of coffee, using the head or having lunch under way

– At slower speeds your journey will take longer allowing more time for battery charging, for engine-driven compressors to reduceyour refrigeration temperatures and for manifold hot water heaters to heat up. This is important because if for example we leave our marina for Oneroa and cruise at planing speed after the engines are up to temperature the journey will take about 90 minutes and this is insufficient time for the refrigeration to becomefully effective. At 8 knots or so the cruise will take about three hours which allows plenty of time. This is not so much of an issue on the following days when refrigeration is already cold

– At slower speeds you can troll and catch a kahawai or kingi on the way (good luck withthat one!)

– Due to lower rpm at slower speeds you’re saving a considerable amount in fuel costs and increasing your cruising range between fueling stops

In addition to these factors by nursing your engines along at low rpm you’re looking after them right? Actually NO – this is quite wrong so read on.

Although Rapport’s top speed is about 21kn fully-loaded, we prefer to cruise at 8-10kn

So let’s focus on reduced fuel consumption and increased rangeeven though weand most people we know aren’t greatlyconcerned about fuel costs, understanding this is one of the cheapest of boating costs.

Here are fourexamples of fuel savings and increases in range (taken from Pacific PowerBoat magazine boat reviews). Note that fuel usage expressed in litres per nm is more relevantthan litres per hr as the former takes into account the shorter distance traveled due to slower speeds.

1. Nimbus 405 13.3m LOA planing vesselwith twin 200hp Volvos and shaft drives:

At 3,000 rpm = 17kn, 95.9 litres/hr, 4.4 litres/nm, 200 nm range

At 1,000 rpm = 7.3kn, 6.5 litres/hr, 0.9 litres/nm, 1,000 nm range – sofuel usage per nm decreases and range increases by a factor of about 5x

2. Absolute Vavetta 14.9m LOA semi-displacementvessel with twin Volvo Penta IPS650 “Pods”, each 480hp:

At 3,000 rpm = 18.7kn, 112 litres/h, 6 litres/nm, 272 nm range

At 1,500 rpm = 7.3kn, 21 litres/hr, 2.9 litres/nm, 564 nm range

At 1,250 rpm = 6.1kn, 9 litres/hr, 1.4 litres/nm, 1,137 nm range – so fuel usage per nm decreases and range increases by a factor of about 4.2x

3. Maritimo S55 17m planing vessel with twin Volvo D13 each 400hp and shaft drives:

At 2,100 rpm = 23.8kn, 226 litres/hr, 9.5 litres/nm, 430 nm range

At 900 rpm = 8.1kn, 26litres/hr, 3.2litres/nm, 1,280nm range – so fuel usage per nm decreases and range also increases by a factor of about 3x

4. Circa 24 –26m LOAdisplacement vessel with twin Scania DI 090, each 250hp @ 1,800rpm and shaft drives:

At 1,500 rpm = 12.3kn, 39.2 litres/hr, 3.2 litres/nm, 3,234 nm range

At 1,000 rpm = 8.7kn, 13.3 litres/hr, 1.52 litres/nm, 6,809 nm range – so fuel usage per nm decreases and range increases by a factor of about 2.1x. Note that at 6.5kn the range increases to over 10,000nm

Theseexamples include displacement, semi-displacement and planing vessels and similar results apply to all standardvessels including single engine vessels and yachts under power(however I’m not sureif this applies with foils.)

The above resultsare based on running both engines and we can see that reducing rpm results in a substantial decrease in fuel consumed per nm combined with a substantialincrease in range as a result of cruising closerto the vessel’s displacement speed where the boat’s hull becomes wonderfully efficient. That’s why long distance cruisers are nearly always displacement vessels or faster vessels cruising at displacement speed. The figures would be even more impressive if I’d compared maximum rpm with idling rpm, but I wanted to compare realistic speeds.

Howeverthere are somedownsidestocruising at low rpm and I want to mentionthese as well as suggesting several alternative options to minimise their effects. These thoughts are based on our own experiences and some internet research as well as discussions with four diesel mechanics over the last several years.

Diesel engines are not designed to be run for long periods at light loading, which is defined as rpm less than 40 per cent of wide open throttle (WOT). On the contrary the suggestedrule of thumb is to run enginesat 60-75 per cent of WOT for 60-75 per centof the time,this 60-75 per centrange beingthe range of mechanics’ varying opinions.

So what happens if you do consistently run at light loading rpm?

At low rpm and therefore lower than optimum engine temperature the piston rings don’t seat so well resulting in faster wear, additional blow-by (more than double thenormal), oil fouling of components such as turbos and carbonisation.Blow-by is the phenomenon whereby combustion chamber gasses consisting of unburned fuel and water vapour as well assoot bypass the rings causing a harmful sludge to build up on the rings in the processand to enter the crankcase. Some blow-by is normal, but increased levels cancontaminate lubricating oil forming a sludge that can partially block lubrication feed lines as well asacids that attack engine parts,often resultingnot only in later engine problems but in significantly reduced engine life.

This is one of several reasons why engines used in commercial vessels generally have a longer life span than in pleasure vessels, that is theirengines are mostly selected according to their intended operationalspeed and therefore rpm.

Another cause of increased blow-by is over filling lubrication oil so never add oil beyond the dipstick marking.

Additionally alternators don’t operatesowell at low rpm. For example aboard Rapport which has24V battery banksour approx 50amp alternators charge at 23 amps at 1,170rpm and 36 amps at 1,510rpm – a 57 per cent difference. At low engine rpm alternators’ cooling fansalso run more slowly causing alternators to overheatparticularly in the early stages of charging when the battery banks need for charging is greatest and the alternators are working their hardest. Leaving the marina this should not be too much of a problem as most vessels have shore powered chargers.

A negative for running slower is it results in more engine hours accumulating for the same distance cruised theoreticallyresulting in an increase in service costs, though practically many vessels have an annual service without reaching their hours of service threshold.

But don’t despair as there are several options available to run vessels at lower speeds without compromising engine wear or longevity, each option having its own pros and cons. 

Read about these options in our next posting.

As
I write this we’ve been in Level 4
lock down for nearly
five weeks
now and hopefully we’ll
be going down to Level 3 next week and 2 the week after. So
let’s hang on in there.                              

From
a boating perspective we haven’t
missed out on
too much as
until the
last few days the
weather has mostly been miserably
wet, windy
and chilly.
Roll on Level 2, warmer weather and the resumption of boating – we
can’t wait!

Here’s
an edited version of an article to appear shortly in Pacific
PowerBoat re
cruising around the Ponui Island area.

In
Auckland
we’re
spoiled for choice of great
cruising
destinations with
about 1,200
square miles of the mighty
Hauraki Gulf and
dozens of islands on
our doorstep, explaining
why Auckland is said to have the largest number of boats per capita
in the world.                                                                              

One
of our
favourite inner Gulf islands
is Ponui. Maori
were the
island’s first inhabitants during
the 1400s and
evidence still remains of 23 separate pa sites. The
island was purchased in
1853 by the
Chamberlin family, who remained
through the generations and still
farm the island to this day. Ponui
translates
as “long
night” and
judging
from the number of cruisers who frequent this area we’re
sure there’s been many an
enjoyable
and long
night
spent here.

Ponui
is about
four miles
long in a
north to
south direction,
one to two miles wide and
indented
with numerous bays and coves offering
at least 20
good anchorages,
well
spread around the
island allowing
cruisers to
find safe
shelter in
all wind conditions. The
highly informative
Royal Akarana Yacht Club Coastal Cruising Handbook (a
must have on board for cruisers) provides
excellent
information on most of these anchorages,
so we’ll
focus on just
three
of our
favourite
areas.

By
far Ponui’s
most popular anchorage is Chamberlains
Bay (also called North Harbour) bordering the northern coast’s
Ruthe Passage separating
Ponui and
Rotoroa Islands.
This large bay offers great shelter in westerlies through to
southerlies and for light north-westerlies and south-easterlies,
although in stronger south-easterlies an
uncomfortable
fetch comes into the bay from
the Firth of Thames.
You’ll
notice that Coastguard have a mooring for their rescue vessels in the
bay’s north-west corner.
Chamberlains
Bay
(note
spelling of this bay is different to that of the Chamberlin family
name) has
no particular hazards except
for its
muddy bottom gradually
shoaling
towards the
southern shoreline. Immediately
to the east are two great sandy beaches easily
reached by dinghy. If anchoring off
these beaches
watch out for the
rocky outcrop between the two beaches and
monitor your depth. Part
of Chamberlains
Bay’s appeal
is that if the wind shifts to the north or east boats can easily
move
less than a
mile across
to
Rotoroa’s South-West
Bay to
shelter.
This
bay also has three
moorings available to rent by prior arrangement at $25 per night. The
Salvation Army ran an alcohol addiction treatment centre here from
1911 until 2005 and
during that
time no
landing was allowed. It’s
reputed that sometimes desperate alcoholics swam out to boats moored
here trying to score a drink. Nowadays
visitors are
encouraged,
but no dogs are allowed as Rotoroa is a wildlife sanctuary with kiwi
and weka abounding. It’s well worth visiting their interesting
Exhibition Centre and your
kids will certainly
love the
nearby brick jail house. You’ll
have to avoid the temptation to leave them there! Take
a walk over the island for spectacular views of the Firth of
Thames and
visit Men’s
Bay and Ladies’ Bay on
Rotoroa’s east
coast – great
anchorages in settled westerly conditions. Formerly
cruisers could only gaze
at these near-perfect beaches from afar, but can now enjoy their
white sand,
crystal
clear
waters and
gnarly
shade-providing
pohutukawa
trees.

Shark
Bay on the island’s western side bordering the Waiheke Channel
isn’t
mentioned on the NZ
5324
Chart for
this area,
but
it’s
the bay to the north of
Oranga
and
Poroaki
Bays.
Oranga Bay is too shallow for anchoring, but take your dinghy in to
see the
shipwreck
on the shoreline with its impressive
propeller and the nearby remains of two boilers. You’ll
also see plenty of rays gliding across the seabed searching
for kai. 

Shipwreck in Oranga Bay on a great early July day

Close up showing the wreck’s huge propeller

Poroaki
Bay can be recognised by
its
several
homesteads
and
protruding western headland providing
protection from the prevailing south-westerly wind. Very
often there’s also a large powered barge moored close to shore.
Between
Shark Bay and Ponui Head to the north are two unnamed
bays with
excellent sandy beaches and shelter from southerly through to
north-easterly
winds, but
be
aware of an unmarked rock south
west of Ponui Head (marked on chart).
The only negative for
this
area is
wakes produced by large motor vessels travelling at speed through the
Waiheke Channel.

Stunning unnamed bay south of Ponui Head

Barge at Poroaki Bay

Bryants
Bay on Ponui’s
north-east
coast is a
settled weather anchorage suitable for northerly through to
south-westerly winds. It’s
well protected
by Scully Reef and
consists
of three small bays, two of which are really
stunning,
together with a large anchoring area outside these bays. This
is an area where we’re often happy to anchor
for several
days and
holding is
good, but be aware of close to shore rocks. About
half a mile south is another well sheltered bay with a fine
sandy beach.

Fishing
is generally good around Ponui, particularly on the eastern side in
the Firth of Thames and
we’re always able to feed ourselves,
however on
the north-western side be aware of the Te Matuki Marine Reserve
extending across to Awaawaroa Bay on Waiheke Island’s south coast.

There
are large signs on Ponui
Island’s
foreshores advising the island is private property and that no dogs,
fires or camping are allowed. I spoke to one of the island’s
three farm
owners who advised
boaties may
land on beaches provided
they observe the above limitations.
Ponui is
home to nearly
2,000
brown kiwi,
descendants
of just 13
released in 1964 and
dogs
and ferrets are their
main predators
so there’s
good reason to ban dogs.
While most
dog owners are responsible a minority
apparently think leashed dogs are not a problem and
that rules
don’t apply to them. However even leashed dogs
can
upset farm
animals and
wildlife
while
their scent
is an issue in bird breeding areas sometimes
causing birds to abandon their nests.

There
is no fuel, water or supplies available in this area, except for wine
at the very
pleasant Man
O’War Vineyard.
On a fine
summer’s day you’ll find dozens of inflatables ashore here
enjoying
the sandy beach and the selection of winery beverages and snacks.
Closest
groceries are at Rocky Bay while for fuel and water you’ll have to
make the eleven mile trip to Pine Harbour marina.

We
really enjoy anchoring in these areas around
Ponui and
hope you will too, but
remember if going ashore to
act
responsibly by taking no dogs, lighting no fires and taking your
rubbish away
with you.

Next
Post will be about cruising at low rpm without compromising your
engines’ performance and longevity.

As I write this we’ve been in Level 4lock down for nearly five weeks now and hopefully we’ll be going down to Level 3 next week and 2 the week after. So let’s hang on in there.                              

From a boating perspective we haven’t missed out on too much as until the last few days the weather has mostly been miserably wet, windyand chilly. Roll on Level 2, warmer weather and the resumption of boating – we can’t wait!

Here’s an edited version of an article to appear shortly in Pacific PowerBoat re cruising around the Ponui Island area.

In Auckland we’re spoiled for choice of great cruising destinations with about 1,200square miles of the mightyHauraki Gulf and dozens of islands on our doorstep, explainingwhy Auckland is said to have the largest number of boats per capita in the world.                                                                              

One of ourfavourite inner Gulf islands is Ponui. Maori were the island’s first inhabitants during the 1400s and evidence still remains of 23 separate pa sites. The island was purchased in 1853 by the Chamberlin family, who remained through the generations and still farm the island to this day. Ponui translatesas “long night” and judging from the number of cruisers who frequent this area we’resure there’s been many anenjoyableand long nightspent here.

Ponui is about four miles long in a north to south direction, one to two miles wide and indented with numerous bays and coves offering at least 20 good anchorages, wellspread around the island allowing cruisers tofind safe shelter in all wind conditions. The highly informativeRoyal Akarana Yacht Club Coastal Cruising Handbook (a must have on board for cruisers) provides excellentinformation on most of these anchorages, so we’ll focus on just threeof our favourite areas.

By far Ponui’s most popular anchorage is Chamberlains Bay (also called North Harbour) bordering the northern coast’s Ruthe Passage separatingPonui andRotoroa Islands. This large bay offers great shelter in westerlies through to southerlies and for light north-westerlies and south-easterlies, although in stronger south-easterlies an uncomfortablefetch comes into the bay from the Firth of Thames. You’ll notice that Coastguard have a mooring for their rescue vessels in the bay’s north-west corner.ChamberlainsBay (note spelling of this bay is different to that of the Chamberlin family name) has no particular hazards except for itsmuddy bottom gradually shoalingtowards the southern shoreline. Immediately to the east are two great sandy beaches easily reached by dinghy. If anchoring off these beacheswatch out for the rocky outcrop between the two beaches and monitor your depth. Part of Chamberlains Bay’s appeal is that if the wind shifts to the north or east boats can easily moveless than a mile across to Rotoroa’s South-West Bay to shelter. Thisbay also has three moorings available to rent by prior arrangement at $25 per night. The Salvation Army ran an alcohol addiction treatment centre here from 1911 until 2005 and during that time no landing was allowed. It’s reputed that sometimes desperate alcoholics swam out to boats moored here trying to score a drink. Nowadays visitors are encouraged, but no dogs are allowed as Rotoroa is a wildlife sanctuary with kiwi and weka abounding. It’s well worth visiting their interesting Exhibition Centre and your kids will certainly love the nearby brick jail house. You’ll have to avoid the temptation to leave them there! Takea walk over the island for spectacular views of the Firth of Thames and visit Men’s Bay and Ladies’ Bay on Rotoroa’s east coast – great anchorages in settled westerly conditions. Formerly cruisers could only gazeat these near-perfect beaches from afar, but can now enjoy their white sand, crystal clear waters and gnarly shade-providing pohutukawa trees.

Shark Bay on the island’s western side bordering the Waiheke Channel isn’t mentioned on the NZ 5324Chart for this area, but it’s the bay to the north ofOranga and Poroaki Bays. Oranga Bay is too shallow for anchoring, but take your dinghy in to see the shipwreck on the shoreline with its impressivepropeller and the nearby remains of two boilers. You’ll also see plenty of rays gliding across the seabed searching for kai. 

Shipwreck in Oranga Bay on a great early July day

Close up showing the wreck’s huge propeller

Poroaki Bay can be recognised byits several homesteadsand protruding western headland providingprotection from the prevailing south-westerly wind. Very often there’s also a large powered barge moored close to shore. Between Shark Bay and Ponui Head to the north are two unnamed bays with excellent sandy beaches and shelter from southerly through to north-easterlywinds, but be aware of an unmarked rock south west of Ponui Head (marked on chart). The only negative for this area iswakes produced by large motor vessels travelling at speed through the Waiheke Channel.

Stunning unnamed bay south of Ponui Head

Barge at Poroaki Bay

Bryants Bay on Ponui’s north-east coast is a settled weather anchorage suitable for northerly through to south-westerly winds. It’s well protected by Scully Reef and consistsof three small bays, two of which are really stunning, together with a large anchoring area outside these bays. This is an area where we’re often happy to anchor for several days and holding is good, but be aware of close to shore rocks. About half a mile south is another well sheltered bay with a finesandy beach.

Fishing is generally good around Ponui, particularly on the eastern side in the Firth of Thames and we’re always able to feed ourselves,however on the north-western side be aware of the Te Matuki Marine Reserve extending across to Awaawaroa Bay on Waiheke Island’s south coast.

There are large signs on PonuiIsland’s foreshores advising the island is private property and that no dogs, fires or camping are allowed. I spoke to one of the island’s three farm owners who advisedboaties mayland on beaches provided they observe the above limitations.Ponui is home to nearly2,000 brown kiwi, descendants of just 13 released in 1964 anddogs and ferrets are theirmain predators so there’s good reason to ban dogs. While most dog owners are responsible a minorityapparently think leashed dogs are not a problem and that rules don’t apply to them. However even leashed dogscanupset farm animals andwildlife whiletheir scent is an issue in bird breeding areas sometimes causing birds to abandon their nests.

There is no fuel, water or supplies available in this area, except for wine at the very pleasant Man O’War Vineyard. On a fine summer’s day you’ll find dozens of inflatables ashore hereenjoying the sandy beach and the selection of winery beverages and snacks. Closest groceries are at Rocky Bay while for fuel and water you’ll have to make the eleven mile trip to Pine Harbour marina.

We really enjoy anchoring in these areas around Ponui and hope you will too, but remember if going ashore to act responsibly by taking no dogs, lighting no fires and taking your rubbish away with you.

Next Post will be about cruising at low rpm without compromising your engines’ performance and longevity.

Great to see the days are finally starting to stretch out a bit and it’s now light from about 0630 until about 1815.

Although official Spring started on 1 September, true astronomical Spring occurs with the Vernal Equinox on 23 September while Daylight Saving commences a few days later on 26 September – bring it on!

Good to see NZ except Auckland going to Level 2 giving the impression the Government is committed to returning us to normality as soon as safely possible. Dare we hope that next week Auckland will go to Level 3 and a week later Level 1? Roll on the Level 2 day so we can get back out on the water and enjoy Spring! The on water boat show due to take place early October has been canceled – another casualty of the lock down which will disappoint the boating community.

As we all know there are no qualifications needed in NZ to skipper a boat used for leisure. Personally I’ve never thought this is a good thing and that skippers of boats over a certain size – say 10 metres LOA or thereabouts should require some qualification, such as a Boatmaster Certificate. Nowadays there is a noticeablyincreasing trend towards much larger power boats and it’s not unusual to see newer vessels in the 20-25 metre range. Unlike displacement vessels, planing vessels of this length put up sizable wakes, particularly at slow planing speeds and we’ve noticed some skippers seem oblivious to this and the mayhem they cause at anchorages for example in the Rakino Channel. I was in contact with Maritime NZ recently who confirmed there is no requirement for any skipper qualification regardless of the vessel’s size if used for leisure. I must admit to finding this surprising as it means that somebody with no boating experience could potentially buy and skipper a 25 metre vessel and while it’s safe to assume most would act responsibly there will always be some that don’t.

We’ve started making our post lock down cruising plans including another trip to the Kawau area, another to the Coromandel Peninsula, Mercury Islands and Mercury Bay plus a trip of several weeks duration to Northland and the Far North. Before we finalise timing we have to await a confirmed installation date for our new deck crane, hoping to have it plus our new RHIB by early-mid November. Even thinking about this gets us excited.

I also have a new writing brief for the annual Pacific PassageMaker magazine due out early next year – an article on what tools, spare parts and chandlery the well equipped coastal cruising vessel should carry. I’ve started researching this, finding it a very interesting subject and already adding a few items to my Rapport shopping list.

Great to see the days are finally starting to stretch out a bit and it’s now light from about 0630 until about 1815.

Although official Spring started on 1 September, true astronomical Spring occurs with the Vernal Equinox on 23 September while Daylight Saving commences a few days later on 26 September – bring it on!

Good
to see NZ except
Auckland going
to Level 2 giving the impression the Government is committed to returning us to normality as soon as safely possible. Dare we hope that next week
Auckland will go to Level 3 and a week later Level 2? Roll
on the Level
2 day so we
can get back out on the water and enjoy Spring! The on water boat show due to take
place early October has been canceled – another casualty of the
lock
down which will disappoint the boating community and be a blow to exhibitors.

As
we all know there are no qualifications needed in
NZ to
skipper a boat used for leisure. Personally I’ve never
thought
this is a
good thing
and that skippers of boats over a certain size – say 10 metres LOA or
thereabouts should require some qualification, such as a
Boatmaster
Certificate. Nowadays
there is a
noticeably
increasing trend towards much larger power boats and it’s not
unusual to see newer vessels in the 20-25 metre range. Unlike
displacement vessels, planing vessels of this length put up sizable
wakes, particularly at slow planing speeds and we’ve noticed some
skippers seem oblivious to this and
the mayhem they cause at anchorages for example in the Rakino
Channel. I
was in contact with Maritime NZ recently who confirmed there is no
requirement for any skipper qualification regardless of the vessel’s
size if used for leisure. I must admit to finding this surprising as
it means that somebody with no boating experience could potentially
buy and skipper a 25 metre vessel and while it’s safe to assume
most would act responsibly there will always be some that don’t.

We’ve
started making our post lock down cruising plans including
another trip to the Kawau area hopefully based around Labour weekend, another to the Coromandel Peninsula, Mercury
Islands and
Mercury Bay basing ourselves at whitianga marina, plus a trip of several weeks duration to Northland
and the Far
North. Before we finalise timing for the latter two trips we have to await a confirmed
installation date for our new deck crane, hoping to have it
plus our
new RHIB by early-mid
November. Even
thinking about this gets us excited.

I
also have a new writing brief for the annual Pacific PassageMaker magazine due out early next year – an article on what tools, spare
parts and chandlery the well equipped coastal cruising vessel should
carry. I’ve started researching this, finding it a very
interesting subject and already adding a few items to my Rapport shopping list.

So we’re back in lockdown again from Weds 18 August and it appears this could last a few weeks. From the boating perspective it’s better for this to happen now than later, as we move into Spring next month. It seems it was inevitable that the delta variant would hit our shores and while it’s all too easy to criticise aspects of how NZ has handled the situation (egthe way in which rooms for quarantine are allocated) our infection numbers are remarkably low. If we had the UK’s infection and death rates, then based on the population difference we’d be having 2,665 new infections and 8 deaths daily. While there are sad stories about people having problems returning to NZ, haven’t these people largely created their own problems?

Back to the subject of Cruising and firstly engine servicing.

We’ve used TerraCat for servicing our Cat 3208 10.4L V8 diesels asthey’ve had a very knowledgeable engineerwho knew our boat well. However he recentlyleft TerraCat and after considering our options we decided to change contractors to Marine Propulsion (MP). The main reason for this is it’s highly desirable to have the same person doing your servicing as they get to know the peculiarities and history of your boat. We weren’t convinced TerraCat could offer this continuity. So far we’re impressed with MP. The engineer who’s now doing our servicing is actually one of MP’s directors (so unlikely to be leaving)and he suggested coming on board a week before the service to familiarise himself with Rapport and discuss our expectations – impressive service. We wanted somebody who will not only change oil and filters, but proactively look for potential issues and provide advice on preventative maintenance. So far we’re very satisfied with our move. For example he found that two pencil anodes in our heat exchangers have not been getting replaced because access is restricted and standard anodes can’t be used. Solution: he’s going to cut some standard anodes down so they fit and then some protection will be better than none. He made suggestions re filter changing frequency to save us cost without compromising performance as well as suggesting we use our spare filters first and replace them with new ones in order to turn the spares over. That’s the kind of engagement and service we want.

Useful tips

1. Barometers

Most of us have nice shiny brass barometers on one of our bulkheads and these should certainly be considered useful beyond ornamentation. So how should we use them?

The barometer’s indicator needle should be reset each morning in order to monitor changes.

If pressure rises or falls 1.6 to 3.5Mb over a 2 hour period it’s warning of a depression.

If pressure rises or falls 3.6 to 6.0Mb over a 2 hour period it’s warning of Force 6 winds.

If pressure rises or falls more than 6.0Mb over a 2 hour period it’s warning of Force 8 winds.

A drop in pressure of 15 or more Mb in a 24 hour period indicates a weather “bomb” is imminent.

As a matter of interest the world’s average atmospheric pressure is 1013Mb

2. Protection from sharp hose clips

Have you ever cut your hands or fingers on the sharp ends of stainless steel hose clamps? I sure have and to avoid this have fitted Clamp-Aid hose clamp safety guards. These are flexible silicone sleeves that easily fit over the ends of hose clamps to provide protection. Cost is about $32 for a pack of 20.

3. Mounting fittings on gelcoat surfaces

At some point we all need to add fittings such as an aerial mount to a gelcoated surface. What most of us do is drill a hole in the gelcoat, put some silicone in the hole and onto the screw and Bob’s your uncle right? Wrong. Silicone has a limited life of around 5 years, so at best water will eventually find its way in to the cavity and migrate into the substrate beneath the gelcoat. The correct way to do this is to drill a hole much larger, in  both diameter and depth than what is required for the screw, fill the hole with epoxy and then drill the screw hole in the epoxy. This will ensure that moisture doesn’t get into the substrate beneath the gelcoat. In any case silicone sealants are not suited to marine applications and we should use marine sealants like Sicaflex 291, 3M4000 or Bostik Simson MSR Construction Adhesive.

4. Paint aerosols

You normally have some paint left in the aerosol after completing your job. In order to re-use the aerosol hold it upside down and press the nozzle until all residual clears out of the nozzle. Then store aerosol upright.

We weren’t planning to do much cruising during August, but hope the lockdown is over so we can start serious cruising again from mid-Sept.

So
we’re back in lockdown again from Weds 18 August and it appears
this could last a few weeks. From the boating perspective it’s
better for
this to happen now
than later, as we move into Spring next month. It seems it was
inevitable that the delta variant would hit our shores and while it’s
all too easy to criticise aspects of how NZ has handled the situation
(eg
the way in which rooms for quarantine are allocated) our infection
numbers are remarkably low. If we had the UK’s infection and death
rates, then based on the population difference we’d be having 2,665
new infections and 8 deaths daily. While there are sad stories about
people having problems returning to NZ, haven’t these people
largely created their own problems?

Back
to the subject of Cruising and
firstly engine servicing.

We’ve
used TerraCat for servicing our Cat 3208 10.4L V8 diesels as
they’ve had a very knowledgeable engineer
who knew our boat well. However he recently
left TerraCat and after
considering our options we
decided to change contractors to Marine Propulsion (MP). The main
reason for this is it’s highly desirable to have the same person
doing your servicing as they get to know the peculiarities and history
of your boat. We weren’t convinced TerraCat could offer this
continuity. So far we’re impressed with MP. The engineer who’s now doing
our servicing is actually one of MP’s directors (so
unlikely to be leaving)
and he suggested coming on board a week before the service to
familiarise himself with
Rapport and discuss our expectations – impressive service. We
wanted somebody who will not only change oil and filters, but
proactively look for potential issues and provide advice on
preventative maintenance. So far we’re very satisfied with our
move. For example he found that two pencil anodes in our heat
exchangers have not been getting replaced because access is
restricted and standard anodes can’t be used. Solution: he’s
going to cut some standard anodes down so they fit and then some
protection will be better than none. He made suggestions re filter
changing frequency to save us cost without compromising performance
as well as suggesting we use our spare filters first and replace them with new ones in order to turn the spares over. That’s the kind of engagement and
service we want.

Useful
tips

1.
Barometers

Most
of us have nice shiny brass barometers on one of our bulkheads and these
should certainly be considered useful beyond ornamentation. So how
should we use them?

The
barometer’s indicator needle should be reset each morning in order
to monitor changes.

If
pressure rises or falls 1.6 to 3.5Mb over a 2 hour period it’s
warning of a depression.

If
pressure rises or falls 3.6 to 6.0Mb over a 2 hour period it’s
warning of Force 6 winds.

If
pressure rises or falls more than 6.0Mb over a 2 hour period it’s
warning of Force 8 winds.

A
drop in pressure of 15 or more Mb in a 24 hour period indicates a
weather “bomb” is imminent.

As
a matter of interest the world’s average atmospheric pressure is
1013Mb

2.
Protection from sharp hose clips

Have
you ever cut your hands or fingers on the sharp ends of stainless
steel hose clamps? I sure have and to avoid this have fitted
Clamp-Aid hose clamp safety guards. These are flexible silicone
sleeves that easily fit over the ends of hose clamps to provide
protection. Cost is about $32 for a pack of 20.

3.
Mounting fittings on gelcoat surfaces

At
some point we all need to add fittings such as an aerial mount to a
gelcoated surface. What most of us do is drill a hole in the gelcoat,
put some silicone in the hole and onto the screw and Bob’s your uncle
right? Wrong. Silicone has a limited life of around 5 years, so at
best water will eventually find its way in to the cavity and migrate
into the substrate beneath the gelcoat. The correct way to do this is
to drill a hole much larger, in  both diameter and depth than what is required for the screw, fill the hole with epoxy and then drill the
screw hole in the epoxy. This will ensure that moisture doesn’t get
into the substrate beneath the gelcoat. In
any case silicone sealants are not suited to marine applications and
we should use marine
sealants like Sicaflex 291, 3M4000
or Bostik
Simson MSR Construction Adhesive.

4.
Paint aerosols

You
normally have some paint left in the aerosol after completing
your job. In order to re-use the aerosol hold it upside down and
press the nozzle until all residual clears out of the nozzle. Then store aerosol upright.

We weren’t planning to do much cruising during August, but hope the lockdown is over so we can start serious cruising again from mid-Sept.