Originally Posted by David M
The reason for running a diesel periodically at full horsepower is to eliminate carbon buildup in the combustion chamber.
My Cummins diesel manual requires that I run my Cummins turbo diesels at 100% horsepower for a half-hour for 10% of the total engine hours. They specifically state that carbon buildup is the reason.
Seemingly babying a diesel by running it at low RPM's all the time or having an over-sized propeller
where you cannot reach full RPM is a good way to shorten the life of your diesel. Diesels prefer to be run hard. I know it is counter-intuitive but they actually last longer. The other huge factor with diesels longevity are to maintain frequent oil changes. These are the two greatest factors if you want your diesel to last. Exercising your engine frequently also helps.
It's just too bad that running your diesel fast with a high load is not the most fuel efficient way of operating a boat....because as you double the speed of a boat you must roughly square its horsepower to do so.
I think that most engine manufactures state that after the engine is run in correctly at various revs for various lengths of time and full throttle also that the maximum revs should not be more than 85% of the top revs of the engine unless in an emergency
Diesel engines definitely don't like tick over.
So if you are on tick over which is not a good idea when you are going to stop the engine rev it up high a few times before switching off it helps to stop/remove the glaze from your tick over and reduces the thermal shock from the cooling
Don't forget to be in neutral out of gear and throttle open slightly when you start the engine.
I have a new Yanmar 3YM20 which has completed 197 hours including the 50 hours run in time (that was a bit boring)
I purposely bought the gearbox
with a lower ratio so that the engine would be working harder, top revs are 3600 85% of that is 3060 I usually run at 2800 2900 where ever I am going but its quite comfortable at 3060. If you have an oversize propeller reduce the pitch
or drop the gearbox
ratio you can only get top speed according to the LWL but it will give you more power.
I use a bit more fuel. but as Onassis replied when a reporter asked him how much it cost to run his yacht. "If you have to ask how much it costs then you cannot afford it"