[Cosfisher]

I've got a 14' deep-v, wood floor with an older (1990) Evinrude 15 tiller on it I picked up this winter. Current prop is 9x10P 13 spline that came it which was previously run at low altitude. I'll be running at 8-9K feet. Anyone have a similar boat and motor with a pitch suggestion? I was thinking of getting a 7 or 8 pitch. Thanks.

 

[K0ALE]

Perhaps you should try it out and see how it goes before you start tinkering with it?

 

[Anteroman]

You can go online and find a prop specialist who can help you out possibly.
He'll need a lot of details, weights etc. Please keep in mind, your engine under full load should be able to attain the maximum rpm recommended by the mfg. for that engine.
Bill

 

[K0ALE]

"Please keep in mind, your engine under full load should be able to attain the maximum rpm recommended by the mfg. for that engine. "

You seem confused, the issue is at lower RPM when the prop presents to much load at a given RPM, at the top end of the power cycle there is lots of power to twist the screw.

 

[Cosfisher]

Koale, I was trying to keep my original post short so I didn't go into a lot of detail. I did take the boat up to SP yesterday and as I expected it was a dog, low RPMS. Had same issue with a 60HP Merc 4 stroke that came from Kansas, I took to Blue Mesa and it was a dog as well. Changed prop to lower pitch, problem solved. Now runs in WOT range. Ideally I want to get RPMS on the 15hp tiller in 5500-6500 range. Called several places online and got varying advice. Just didn't want to buy and try several props if I could avoid it. I realize it can vary for every boat that's why I was wondering if someone had something similar.

 

[koldkut]

I've got a 20hp merc on a 16' starcraft, 9 pitch for high altitude and 13 for low altitude.....fwiw

 

[Cosfisher]

Thanks koldcut....when you say low altitude would you be meaning like Pueblo?

 

[Mtntop285]

Hi Cosfisher, I have a 1990 25 hp 2 stroke merc on a 14' lund aluminum and run a 9.5 pitch at 9000' and above with no issues at WOT. My engine is supposed run at approx 5800 rpms at WOT. Call Jim's Prop Shop in lakewood, the guy is a genius when it comes to props. I also run a 11.5 pitch cupped prop at 5200' with no issues. Tried a 13 for fun at 5200' and it pushed the boat, but not as fast.

 

[Cosfisher]

Thanks for the response folks looks like I'll have to come down 2 or 3 pitches. I'll call a few local shops tomorrow since most were closed today. Appreciate your help.