80/81 70HP Chrystler. Can reach high RPM when in nutral, but when in gear max is 1500. Last weekend we were running the boat at approx 18MPH (Verified by GPS.) This weekend with the same prop max speed is only 10MPH. I know the prop is the wrong size however, with no changes to the motor or the prop in one weeks time the max speed dropped in half? Also the motor will stall at WOT only when in gear. Compression is 150, 150, 155. Ideas?????
