Quote Originally Posted by fox river rat View Post
Well, talking to an aviation friend, I need to adjust the prop so the engine only spins at 64-6500 r's. Pitch is too flat, that is why it's running at 7150. That's suppose to make a big difference. This same engine was flying a plane before I got it, same exhaust, etc. So I should be OK. I'll check back in a couple days.

Thanks for suggestions.
I wouldn't stick to a certain or targeted rpm, you need to find out where that motor likes to be run. I'm sure it's just a matter of getting the pitch set, I was thinking belt slippage until I seen that it's a gearbox.