According to the repair and parts manuals, my 1998 40 hp force is identical to the same year 50 hp motor except for the high speed jet in the carb. Thinking I could get 10 extra hp , I changed the jet. I learned that aparrently it's not that simple. The motor ran real rich and would not go over 3000 rpm. I think it needs more air. Anyone out there know what the difference is ? Maybe something in the reed valve system ? How about the exhaust system ?