My 1980 Cat 30 still seems to have its original propeller, but the 11 hp engine was replaced with a Perma 30 hp diesel. I'm thinking the engine doesn't like never really working very hard just to spin that anemic prop, and so it carbons up even at 2600. Looking for advice on replacing the propeller. I'm just a Chesapeake Bay day sailor, no racing. The motor is only to get out of and into the bay from my river marina.