I got a used 2000 Ficht 150 and rigged it on my boat. I was told to put a 14 1/2x 19 prop on it. I rigged an aluminum prop on it, but i can only get 4300 RPM's. The engine runs great, idles great, starts immediately. But I know that I should get 5250 at WOT. It's on a 1976 SeaCraft 20...