650 prop size

[Hookem Dano]

My 1969 65 hp 4 cyl 650 Merc has a 3 blade 15 inch pitch prop. What pitch could i go too for more speed. It's on a 15.6 fiberglass, right now it only go's 27 mile per hr. Would like to hit 30-35 if possible. Thanks for any Info

 

[WillyBWright]

Re: 650 prop size

It's kinda guesswork, but I'd expect a 17 to be a good average prop, your 15 to be a good pulling prop, and a 19 for speed. It depends on a number of factors, so this isn't carved in granite. I would expect either the 17 or 19 to get you up to that speed. Mostly you want to get 5500rpms out of your motor at full throttle with an average load. That gets your full horsepower.

 

[Solittle]

Re: 650 prop size

What is your rpms at WOT now and what is the recommended max WOT for your motor? Where is the cavitation plate relative to the bottom of the hull? What is the condition of the present prop?<br /><br />We can point you in the right direction with this info.

 

[Hookem Dano]

Re: 650 prop size

The cavitation plate is right even with the bottom. I don't have a tach just a g.p.s. I'll try a 17-19 pitch and see what happens. Thanks for the replys.

 

[JB]

Re: 650 prop size

Slecting a prop is like buying a pair of shoes, Dano.<br /><br />The ONLY way you know it fits is to try it.

 

[Hookem Dano]

Re: 650 prop size

Right on JB........... Thanks, I'll start trying the shoes on.

 

[Solittle]

Re: 650 prop size

You could start by having your prop repitched and cupped. You will be shooting in the dark without knowing rpm at WOT though. If you over pitch you will be lugging your motor - if under you could overspeed it.