Propeller clearance: between the propeller blade tip and the hull, should be at least 15% of the diameter of the propeller, Ie. 20" propeller should have a tip clearance of 3".
We changed from a Saylor propeller which has narrow thin blades, less drag under sail, less control under power, to a Dyna-Prop, which has shorter thicker blades, better control under power and slightly more drag under sail.
Personal preference varies, being diesel engine mechanics and sailors, we tend to favor close quarter docking control over a slight reducton in boat speed under sail.
Best wishes,
Marty Chin
Bay Marine Diesel