Either one will work
The three blader will cost more than the two blader and will provide better acceleration. The two blader will cost less and will have SLIGHTLY less drag under sail.Talk to the Gori people and find out what they recommend. They have put lots of their props on Catalina 36s (both with the M35BC and the M25XP), so make sure you tell them which engine you have.Several people on this list will rave about the Max Prop, the Auto Prop, the Flexofold, or the Martec. A few even talk about the Kiwi. All of these props will work, each has it's advantages, but the most important thing to remember is that you need to get a prop with the correct diameter and pitch. ANY prop will get your boat to hull speed as long as the diameter and pitch are correct (that is assuming that your engine has enough power, and yours does).On my Catalina 320 (with a 27 HP Yanmar), I have the two bladed Gori folding prop, and am very happy with it.SteveAlchemist C-320