Well I got the tach in and put it on the engine this past weekend and she is only taching out at 3800 rpm at the dock.. on the water with the boat moving the rpm’s do come up more than I would have thought but only to 4200 rpm. For an engine that is supposed to get 5500 rpm for nominal 6hp at the prop this isn’t acceptable. I think there is something wrong with the engine even though it has no violent symptoms of being broken other than lack of power. Tohatsu is now saying they think the prop is too far down in the water and want me to move the engine mount back up two inches to the stock height. I will do so but after this I am getting tired of playing with it. They have told me that lowering the pitch will increase the rpms but a while back they said it will only give about 300 more rps which will still be 900 rpms below nominal and 1400 below max rpm at 6000. I could have paid many hundreds less for a 4hp engine rather than buying a 6hp if I hadn’t wanted more power than I had before. This engine is still running weaker than the old early 90’s 4hp 2 stroke Johnson..
Scott-
It could also be a prop mismatch. If the prop is spec’d wrong, it won’t be able to get to maximum RPM.
It is confirmed the correct stock prop. I can go from it (8 pitch) to a 6 pitch and it would give me about 300 more rpm according to tohatsu. That still lacks a lot. To be honest I think the electronic ignition advance is broken or they put this thing together with the jets for the 4hp engine. The 4hp 5hp and 6hp are identical engines just different jets in the carburetors.