I have a 24' Sweet water pontoon boat with2- 23" DIA pontoons ( dry weight 1920lbs) with a f70a yamaha 4 stroke ( wot range 5300 to 6300 rpm ). Test weight with motor , gas , gear and 2 people is apx 2750 lbs. Prop #1 is 13 5/8 x 13 . WOT is 5400 to5600 rpm speed 23mph gps . Will not reach 6300...