What prop for a 20 ft. JIC Mfg. pontoon, 40 hp mariner

[jajenson]

Last year I bought a used 20 ft. pontoon, with a 1995 40 h.p. Mariner on it. It came with a 10 3/8" X 13P prop. I need to get a new prop, and I'm not sure if I should go to a 4 blade. If I do, what pitch and diameter. What are the advantages/disadvantages. I'd like a little more top end. If I stick with a 3 blade, should I stick with the same pitch, and go bigger in diam. or just go with more pitch? I don't remember what my wot rpm's were. My top speed with 2 people, and 6 gals. of fuel was about 15 to 17 mph. With 6 people and 6 gals of fuel, about 13 mph. Any help would be appreciated.
Thanks,.
John

 

[WillyBWright]

Re: What prop for a 20 ft. JIC Mfg. pontoon, 40 hp mariner

13 is for a planing boat. WAY inappropriate for a toon! They make pontoon props for those in 8", 9", and 10 1/2" pitches. I'd aim for the 9" with heavier loads, but the 10 1/2" would work well with lighter loads. 8" is too shallow.