prop selection

[boatin12]

hi everyone my question is this i have a 1973 65hp motor and i live in colorado which is a higher elevation what size prop should i be running?

 

[rndn]

Re: prop selection

More information is needed. What boat is it on? What is the current prop? What are the current rpm's at wide open throttle(WOT)?

 

[boatin12]

Re: prop selection

its on a 15 1/2 foot tri hull rpms are at 5500 thanks for your help.i have 3 differnt props 14x11,14x13 and 13-1/4 x17

 

[rndn]

Re: prop selection

I also need to know what make is your motor. Evinrude, Mercury, etc.

 

[boatin12]

Re: prop selection

oh sorry its a 1973 65 hp johnson powershift II loop charged and right now i am using the 14x13. would the 13-1/4x17 be to hard on my motor?at high elevation

 

[rndn]

Re: prop selection

You would be adding 4 inches of pitch would would reduce the rpm's by around 800. I can't seem to find what the suggested rpm's at WOT should be for your motor, but I would have to guess the 800 rpm reduction would bring it too low.
Does anyone have the suggested rpm's at WOT for this 3 cylinder 65 hp 1973 Evinrude?

 

[boatin12]

Re: prop selection

well thanks for your help maybe ill just give it a try anyway.

 

[K.P.]

Re: prop selection

If you are turning 5500 RPM's now with the 13 pitch, you'll be wasting your time and energy with the 17 pitch. You'll have very slow hole shot and slower top speed because the RPM's will not be up where they should be.

The boat probably was originally equipped with the 17 pitch which the owner found did not work well. The 13 pitch worked better but because the boat is smaller, the 11 pitch should be used when you have a full load of people in the boat or pulling a skiier. Although I am assuming all three props are in good condition without excessive knicks in the blades.

 

[boatin12]

Re: prop selection

thanks k.p. i really appreciate your help!