Originally Posted by Don Lucas
I agree and run mine the same way!
Hell I don't even know what 80% load on my engine is. I run mine based on sound, it is pretty apparent from the sound where the engine is most happy at. But run it up hard a few times every few hours and allow it it cool down prior to shutting down.
I think that other than operating your engine corrently and changing the oil
etc that how long the engine lasts comes down to luck! On my engine the luck line lines up with the 20,000 hour mark I hope.
Diesels have something called a "power curve" or something similar listed in their manuals
. They tail off and flatten near the top of the curve, so to find 80% for your model, you find where the curve crosses the "80" with the associated RPM
. It might be 2,100 RPM
or 2,600 RPM if somewhere past 3000 RPM is the maximum.
Maximum revs are fine for stopping in the shortest distance, but generally is neither fuel
nor thrust-efficient, given that those last few hundred RPMs do not add a lot of thrust.
Of equal if not more interest is the other chart you'll likely see for your engine, which relates fuel consumption
to RPM for (assumed) flat water
. This is going to be less than 80% in most cases, but well above 50%.
If you plan on motorsailing, this is the sweet spot for range and economy. The surprising thing for most people who motor
sailboats for longer distances is that the difference between fuel consumption
at, say, 5.2 and 5.5 knots can be quite significant. You soon learn where the engine's thrist, your personal time and wallet factors, and the RPM readings intersect.