I currently have a Rebel SS 3 blade prop. I have a 1989 150 hp evinrude outboard. The max RPMS I can reach is only 4700 rpm @ WOT. My max speed is only 58 mph. The boat is a 1992 charger 180 TF. 18 feet long. 3 batteries. 20 gallons of fuel. 500lbs persons and gear onboard. The motor...