Prop pitch question?

I’m looking to replace my prop on a mercury 35. The current prop has a pretty good size ding in it. Right now it has a 10 3/8″ diameter with 13″ pitch. Wide open RPM was running around 4500 last year, so I’d like to get it up to around 5500 rpm. I’ve read you need about 1″ per 200 RPM decrease in pitch. So I’m thinking I should drop the pitch to about 9″, does this sound right. What about diameter? Most of the 9″ pitch props I’ve seen online are 11″ to 12″ diameter. How will the diameter affect the performance assuming I have enough room to mount one that big. Any advice would be appreciated.

I think you have more issues than just too large of a prop. Sounds like a tune up is in order first. If you still aren’t pulling enough RPM I’d look at a 10 or more likely an 11 pitch prop. I’ve run a number of 25 hp outboards and they all spun a 10 diameter x 11 pitch with out a problem. Your 35 should do the same.

Thanks, I thought that drastic of a pitch change might be indicating more than the wrong prop pitch. The guy I got it from was kinda of a goober so I wasn’t sure if he had put some goofy prop on it.

Yeah, a 9″ pitch sounds pretty shallow. In regards to diameter, from what I have read, the diameter does not affect the operating speed too much, within reason, of course. If you’re talking about an inch difference in diameter, I doubt you’d notice (as long as it fits ).