Join Date: Jan 2007
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Rep Power: 11
Find out what model Yanmar you have, (ie 2GM,2GMF, 2GM20, #GM, etc), then someone here can tell you what the max recommended rpm is, and what the max continuous rated rpm is. Off the top of my head 4000 seems a bit high - my 1982 2GM has a max of 3600.
What speed were you going when it smoked? You likely were near / at hull speed and will not go faster, even if you had a bigger engine!! I think you were pushing the engine a bit too far, and trying to get more speed than it will do continuously.
Engine should be good for years to come. Great that its starts easily!!
As others have said, get a manual, or download one - get familiar with the engine for troubleshootingm, fuel filter changes (and necessary priming), etc.