My 1981 C&C 34
has a 3GMD, raw water
cooled, with about 2200 hours on it. The tag on the engine says 20hp at 3400 rpm.
The owner previous to me had a 16x10, two blade Martec on it. That worked okay but we do a LOT of motoring in Puget Sound
so I replaced the Martec with a 14x7 Campbell Sailor.
I am very happy with the Campbell prop. It is much smoother, allows me to get to 3400 at full throttle, and it sails
well. I cruise
about 5.5 kts at 2600 rpm.