Have about 350 hrs. Seems to run good. Per Yanmar, this engine has a max. rpms under load of 3800. I can only reach about 3700-3750 according to the boat tach. under load. This is the best that I have ever done. Comparison with a hand-held photo laser tach at 3800 rpms in neutral, the boat tach is reading about 150 rpms higher than the hand held. Therefore, I need to gain at least 200 rpms in order to reach 3800 max rpms under load. I usually run the engine (in small power boat) in the range of 2000-2500 and try to run at least 5 min. or so at 3000 rpm whenever I am out. I know that I am over-propped and should probably for next season have the pitch reduced an inch or so to gain 200+rpms or swap the prop out with another. Question: What damage or long-term effects does being over propped have on the engine given how I currently operate it? Just how critical is it to achieve max rpms under load? I never get any black smoke just white smoke at times at idle. Please advise. Thanks, Jim