FYI - Have a 1976 Nova Wellcraft (21' - cuddy at 3750 lbs) with Ford 302 (188 hp). Could not clear 3500 rpm with 15-square prop (came down from 15 x 17). Covered everything else (tune-up,clean fuel lines, water separator, secondaries wide open, etc,), but no 3800 - 4200 rpm. Getting 39 mph @...