What is the issue?Vehicle engines are subject to continuously varying RPMs and loads. Boat engines by contrast tend to remain at static revs for long periods and are often unloaded. They spend much of their lives ticking over and a large proportion of this is immediately after a cold start. The latter lifestyle is far from ideal for a diesel engine and a vehicle offers a much healthier environment.
This is because a diesel engines inherent design is to be loaded. As a result they tend to slightly over-fuel when lightly loaded as only a small percentage of its output is being consumed at any given RPM. This over-fuelling cause's incomplete fuel combustion and a resultant build up of carbon deposit or coating on the piston, rings and bore/liner of the engine. When the engine is cold, or running at less than the normal operating temperature of 185 degrees F, it is a time when it is completely subject to incomplete combustion.
Why address this?Extended periods of light or no-load engine running will result in a very high engine wear rate and lack of efficiency. The engine will smoke, power will decrease, and compression will reduce causing increased fuel consumption. As exhaust ports and valves foul up there will be very high of pollution / emission. This leads to cylinder bore glazing and high lubrication oil consumption plus ring damage.
It may sound surprising but a practice of light or no loading could reduce the service life of an engine to one quarter of its capability.
How to address this?Load the diesel engine. It is essential for the life of a diesel due to incomplete fuel combustion.
If you are running the engines to charge the batteries on anchor or alongside a quay place the boat in gear so that it is loaded by turning the propeller against the warps or ground tackle. This is particularly important when starting from cold. The quicker the engine gets to full operating temperature the less the incomplete combustion due to cold running there is.
If you have been operating the vessel for a period of low loading you can reduce the carbonisation by running the engine hard so that it gets hot. As the engine temperature rises carbon traces can be burnt off. Some lorry drivers even go so far as to add petrol to the diesel every 1000 hours. A ratio of petrol to diesel of 1:100 raises the operating temperature so that the engine decarbonises and they pass emission regulations.
With thanks to:Michael Harpur, Yacht Obsession.
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