5hp and 6hp merc question - The Hull Truth

wooly15 · 07-29-2008, 04:42 PM

I recently picked up a 2004 Merc 5hp four stroke tiller and started doing some research. I compared it to the same year model 6hp and noticed that the only difference was higher RPMs on the 6hp. Is that all it takes to make it qualify as a 6hp? If so, whats the point of offering two engines with such a subtle difference? I guess what I'm getting at here...is there an easy way to modify the 5hp to that extra HP?

A1 Outboard · 07-30-2008, 06:26 AM

Legality wise, the Feds have laws against modifying or doing anything to change the emission outputs of certified motors, unless used in a racing event. www.epa.gov

Usually there will be slight differences to get the different hp ratings, when one has a higher rpm, then usually there are tuning changes such as in the intake or exhaust systems, timing, and fuel flow.

You can contact any number of high performance shops that modify motors but I doubt they would take it or you would want to spend the money required for 1 hp gain that would barely be noticeable on a boat.

wooly15 · 07-30-2008, 03:27 PM

Thanks for the reply....

I agree, a 1 hp gain is not something I would spend money on. I was just curious if it was just an idle adjustment or rev limiter that I could tinker with at no charge