Help With Prop Selection!!

kneeslider74 · 10-17-2009, 09:24 PM

I picked up a 30ft wellcraft catamaran with twin 454's 500hp each with high lift cams a roller goodies. Kaama Surface Drives. I have to replace the props and am curious where to start, 3,4,5 blade and pitch. Boat runs 80 with what is on it but rpms are a bit low, 3850. I am assumin a lower pitch or smaller diameter would help but dont really know the egg beater details as I am a converted jet guy. I appreciate any help I can get as long as it is not speculation.. thanks agian
Al

Craney · 10-18-2009, 07:10 AM

What props do you have on it now??

Griff · 10-18-2009, 12:53 PM

Your rpms are way low. You need to go about 4-6" in pitch smaller.

BTW, egg beaters are outboards

divebum · 10-21-2009, 12:37 PM

Your prop pitch is the amount of travel in inches per revolution so if you have a 22 pitch prop in one revolution the boat will move 22 inches in the water, there is a loss factor but if you know what your other props were doing your can get a general idea of what that is. i think it's Mercury Marine's home page has a link to calculator that can calculate this all out.

kneeslider74 · 10-22-2009, 01:15 PM

I am tring to figure out what pitch are on the boat. All I know is they were 4 blades and port had a 2 inch hairline in it with a stamp of KME 986// J 655 & J 340. The Starboard prop has KME987// J 340. The ratio is 23 outer- 35 inner on port and 26 outer and 35 inner starboard. They are counter rotating but not a clue as to the set up