Originally Posted by Minnewaska
Max rpm should be in the engine manual. You raise a very good point. My TAMD31 has about a half dozen variants, signified by a following letter. All but mine have max rpm at 3800, but mine is only 3000. I had one engine shop hear the 31 and assumed the higher rating and went down a rabbit hole trying to resolve an issue.
The only data that I can find in the manual is the maximum output rating of 39hp at the crankshaft at 3,000rpm. It gives a propeller speed of 1,293 rpm and a reduction ratio of 2.32. Can I multiply one by the other to get max rpm (which would make 3,000 rpm)?