If you have the outboard incorrectly proped for the application and cant get to the peak power RPM how is that the manufactures fault again?
It is propped to the lowest pitch prop made for the engine and it can't reach nominal rpms. Um... ok... lets see... yeah I do blame the manufacture.
Both the old engine and the tohatsu are rated at hp out at the prop. This is what Tohatsu USA told me even. So 4hp is more powerfull than 6hp now. I guess math is not a strong point for me.
All I know is that the engine propped with the lowest pitch prop made for it wont reach it's nominal rpm. My old 4hp engine will push the boat faster than the new 6hp engine.