New to me 16 foot hewes craft sea runner. Original prop frozen. so I ground it off.Original owner used a 13.25x17 prop and got 30 mph loaded or not.iv'e got an old 15 spline 21 inch. Probably too. much pitch but not sure. boat will average about 2500 pounds. I'm adding a tach as it's a must. Just trying to narrow the gap between props. Thanks