2-blade Prop
You're likely to get many opinions, but start by consulting your Yanmar dealer or the Catalina factory guys. Tell them the specific boat model/year, engine type, and transmission type/ratio. They can use that information to help find a starting point regarding the prop diameter, pitch, and blade shape. You then should run some sea-trials to ensure that combo works for *your* boat, engine, and transmission. Yopu should do this with a clean hull to minimize drag. The pitch might have to be adjusted slightly to get a better match to the optimum engine power/torque RPM. --RonD
