Catalac 8m OB 2-Stroke 45hp prop pitch & diameter question..?

[paularey]

Was hoping someone here might know or have a good recommendation for me about re-propping my outboard..? But it’s not exactly a typical set-up! It a long shaft and hangs on the back of my 27 ft sailboat/catamaran (8m Catalac). The motor is a Mariner 45hp 2 stroke Ser # OB298425, 1988 is as close as I can figure. Anyway it was thrown on stock straight out of the box some time ago with know thought about the configuration of the boat/weight & its application! I know they install different pitch props on house & patio boats, props of a lower pitch, larger diameter, & 4 blades sometimes than typically used on lighter boats. I am looking for something that will run a little more efficiently and work well at slightly lower RPM than wide-open throttle..? The boat clips right along when motor sailing but full throttle isn’t required but when there is no wind I’d like to get the most reasonable power transfer out of it as possible. Is there such a prop in this realm? The boat is a Catamaran with a water line approximately 27ft long and a dry weight of 6200lb. Any help on this matter or advice on whom to talk with is greatly appreciated.

[ted655]

you may be charting new waters here. WOT & max rpmsare how most props are chosen.
Rules of thumb may be your only choise. We know a 4 blade is more power. We know a low pitch is more power. Diamater will depend more to your desired speed & rpms.
I'd first see what types/sizes were available for that OB. Then the choises will come down to a few.