Seems like trial and error are the best method for prop selection. What about just using a tach to obtain the best rpm? If the usable rpm, lets say is 12k is given, would using a blade to achieve peak rpm be an acceptable method, or do you look for a prop that will perform the best at a given rpm. Example. I have a Seamaster that takes more power to lift off the water. Hence, more thrust at near full throttle. Once in the air, I run generally 1/2 to 3/4 throttle, and need less thrust. and what is the difference in thrust using 2 blade vs 3 blade?