Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp
It appears that a lot of people look at the specs for an engine, when they see another engine with the same displacement but rated at a higher Hp you can see the sparks and smoke coming out of their heads. They think that a jet change, or a 1/4 turn of some screw and they will suddendly get horsepower the manufacturer denied them. If only it were that simple. Sometimes it is only a larger carb. More often it is different porting in the block, along with exhaust tuning, different heads, reed and manifolds. To make more HP an engine has to turn higher rpms. The forementioned differences allow the engine to inhale/exhale better at higher rpms. The tradeoff is a torque curve moved to a higher rpm range, resulting in less torque and Hp at lower rpms. So taking 2 engines of the same displacement say 100 cu in, one rated 90 hp the other 140, the 90 will have much quicker accelleretion out of the hole than the 140 but once the 140 has reached higher rpm it has the advantage from the less restrictive breathing and will over take the 90.