proper proppeller size

[willy10]

i have a 1978 70hp evinrude and i am running it at about 6000 feet above sea level and am wondering what size of prop i should be running on it. i currently am running a 13 3/4 x 15 and it doesnt seem to fire out of the hole or gain to many rpms. any help would be greatly apreciated

 

[Bifflefan]

Re: proper proppeller size

Are the carbs adjusted for high altitude?
Running it on what? A 20' glasser or a 12' alum? Maybe you just dont have enough motor.
A 15p on that should run fine on a 16' glass or alum boat. If thats what you have then the prop is not the
problem.

Also, you only need post the question once. Dont post in multiple sections, use the one that best fits the question. This one should be in the prop section only.

 

[wilde1j]

Re: proper proppeller size

If carbs have not been rejetted (from SL), that needs to be done. You are about 20% down on HP at 6000' MSL, so lower pitch (than Sea Level) may be needed. RPM should be ~ 5500 @ WOT.