I've read that a two blade prop is more efficient than 3 at the same rpm. It gets a cleaner bite of the water.

OTOH a 3-bladed prop has more surface area and is less prone to vibration problems. It should be able to develop more static thrust, with more surface area, but then again you only have so much hp and torque from a given engine.

Bottom line: Its not an easy decision. Given the cost of props I wouldn't rush out and buy one just to try it. You've got to be solving a problem.