Further to Ski's point above, Yanmar rates ALL of their engines for continuous duty at 200 rpm off of top. Everything from a two cylinder sailboat engine, my 6LY 370 hp turbocharged and after cooled engine and especially the notorious 6LY2 440 hp engine that will quickly self destruct at that rpm are all rated continuously at 200 rpm off of top.
That continuous rating for my engine is 290 hp at 3,100 rpm (3,300 is rated). 290 hp is 55 hp per liter which is about 20 hp higher than what most pros (Tony Athens) recommend for decent engine life. I say decent, because it is a compromise. Best life is probably half of that. OTOH, sportfishermen often run the snot out of their DD TI engines and are happy to get 2,000 hours between rebuilds. But I suspect that we trawler owners expect more engine life than that.
But Yanmar finally got some religion when they issued their propping specs some years ago. Even though my engine is rated at 3,300 rpm they recommend propping it to a minimum of 3,425 rpm. That gives them a 325 rpm hedge against their 3,100 rpm continuous rating. Not enough, but better than 200 rpm.
David
Rating the engine and saying to run it that way constantly are sometimes two different things. Our only Yanmar is on RIB's and while rated at 180 hp is not run at -200 or anything close.
I agree with them grouping engines into manuals the way they do being bad.
Our manual says nothing about running after break-in. It has two break in periods. During the second of those periods (10 to 50 hours), it recommends against extended cruising at low speed, recommends running it primarily at -400 RPM or about 70% load, with 10 minute runs at -200 RPM and 4 to 5 minutes at WOT every 30 minutes.
Now we talked with them as well as others. On a RIB it's certainly not practical to run at 70% load all the time as that's around 30 knots and not the purpose for which we use it. The advise we ended up with which made sense to us (only for our application though) was that after running it 30 minutes at low speed to run it 4 or 5 minutes at 70-80% load. We typically run around at 15 knots or so, some at around 25 knots but then do our 30 knot runs. If we use it for 6 hours or so in a day, we'll typically open it up to WOT for about 2 minutes.
I admit to their guidelines, or lack thereof, not being very useful. They also tend to not even realize that some of their engines are not in trawlers but in boats that only weigh 2400 pounds including the engine.
Regardless, the most hours we have on a Yanmar diesel at this point is about 120 hours so we can't speak as to what kind of durability we might have running as we do.
We don't have props and they will turn at WOT full RPM of 4000. We have no continuous rating on them as they're really not designed for continuous running in our situation.
That said, on every other diesel engine we have whether propulsion or generator we have far better information in the manual plus available from them. That includes MAN, MTU, Cummins (Onan), John Deere (Northern Lights), and Kohler. I can't speak as to anyone beyond that.