Prop Size??

[sebas54]

Hi, I have 22' aquasport merc. 4.3l

Last season I was using 15x15 prop, which over revved the engine by around 500rpm. I purchased a 15x17 and installed it but once I got to the ramp it hit some rocks and got banged up bad. I never got to use it. My friend gave me a 15.5x18.5 and it under revved by 400rpm. WOuld this cause the engine to overheat because I was running on the hot side at high rpms?

Should I get another 15x17? What I was thinking is:

15x15 500rpms over
15.5x18.5 400rpms under
The 15x17 should be almost perfect. 50 rpms off?

Thanks

 

[steelespike]

Re: Prop Size??

I don't think it would run warm.More likely a cooling problem.A 17 should put you close to what you want Wouldn't hurt to give the actual rpm and tell us the rated max rpm;just to be sure we are all on the same track.

 

[sebas54]

Re: Prop Size??

4400-4600 rpm rated max rpm

15x15 prop 5000rpm
14.5x18 prop 4000rpm

 

[sebas54]

Re: Prop Size??

If I stay with the 14.5x18 prop will there be any ill effects? If I never run it WOT?

Thanks

 

[JJJ]

Re: Prop Size??

Most 4.3's rpm range is 4400-4800 and you want to be closer to the 4800. 4000 is too low and isn't good for the engine, even if not at WOT. You are just really lugging the motor through the whole range..

 

[bowman316]

Re: Prop Size??

go with the 17.
those numbers sound about right, you loose 200 rpms for ever inch in pitch you go up in.