Before I chose the
Beta Marine engine for our
boat, I looked closely at the
Yanmar, going so far as to read the owner’s manual from cover to cover. In the
Yanmar manual, it recommended that prior to shutdown, the operator should increase the RPM to Wide Open Throttle (in neutral) and quickly back to low idle five times. This makes sense to me, especially if the engine is equipped with a turbocharger.
However, I feel that operating a modern
Diesel engine at low loads/RPM has little effect on its durability or length of
service between overhauls. If you corner a licensed
Diesel engineer, he or she will likely say that modern Diesel engines are designed to deliver reliable
power at a wide range of operating conditions and speeds. Look at construction
equipment, especially cranes, whose engines often idle for days at a time - those engines don’t have any special designs nor do they have a significantly shorter lifespan. I used to make my living as a heavy
equipment mechanic (primarily agricultural and earth-moving equipment, but I also did a hell of a lot of
work on over-the-road truck-tractors) and I also served time as a
service manager for a busy truck-tractor dealership in western Missouri. Even though this was many years ago, the percentage of
work orders that involved internal engine failure or problems was very low, despite the fact that many of the engines were often used hard or sometimes had a very light-duty application.
My suggestion is to run your engine at whatever speed makes you comfortable and as long as you have regular
maintenance, adequate
oil pressure and
coolant temperatures within specifications, it should give you many hours of trouble-free operation.
Fair winds and calm seas.