Originally Posted by ltgoshen
My 1981 C&C 30 MK1 manual says 6.7 kt at 3400 rpms.
Well here is the thing the last owner put a folding prop on because he raced. I here a thud when I engage the prop. It don’t back up very good. And I can only get around 2,000 rpms? If I push past that very long it starts wanting to smoke black smoke? Like ,I may be pushing too hard on the engine. any advice?
It looks like you have a Martec prop, which is the worst of the folders. I had one of those on my boat, until I found a good deal on a used Gori prop, which is the same idea except there are gears so the blades open and close together. It is definitely smoother, and reverse is much improved; still not great, but better than the Martec. It definitely sounds like the prop isn't sized correctly for your engine.