I'm running a 1997 Johnson Sailmaster with the standard 10 x 7 prop. (I think) on a full keel sailboat that displaces 6400 LBS. on 18'1" LWL. I've calculated that my max. hull speed should be 5.7 knots & that theoretically 9.3 HP would be all I would need to push the boat to hull speed. However...
