Re: Overpropped; What to do?
The way I understand it there are two separate items. Your prop should be pitched allow you to get up to 90% of the max engine power (SHP). You can find that RPM in a curve provided by the manufacturer but using 90% of max rpm I think works as well. Cruising speed should be at from 70 to 80% power. The reason for this is that the diesel wants to be at that temperature to fully burn it's fuel. Operating at lower powers results in carbon build-up and fouling of the cylinders and valves. The most common diesel problem with sailboat auxiliaries is not operating long enough at power to get to the proper temperatures. Typically they're started up to get underway then shut down before getting up to temperature with the reverse on return. This kills diesels.