I just baught a 79 Formula 255 liberator with twin 260 mercruisers with R drives. Boat is in pristine shape with 350 original hours on the motors. It has 4 blade 20 pitch aluminum props. It ran 51.3 MPH at 5700 RPM's and jumped on plane instantaniously. I would like to go to 3 blade stainless steel props to get better speed and bring the RPM's down a little. Both props spin clockwise as you are standing behind the boat. Is this considered clockwise or RH? The shafts are 15 spline. Can I uses alpha props? Any advise would be appreciated. Rob