help with prop

[jnk111]

I have a 1988 17' bayliner cuddy with a 1988 85hp force. I am currently running a 13.5 - 17 aluminum prop. At WOT it is at 4200rpm and around 32-33mph per speedo, the operating range is 4500-5500. I need suggestions as to what pitch prop would get me in that range, I really can not go any larger diameter because the exhaust is above the prop and there is not a whole lot of room. I mainly use the boat for cruising, in the future I may want to pull a tube.

Thanks,

Joe

 

[rndn]

Re: help with prop

Typically one inch of pitch will equal 200 rpm's. Add one inch of pitch and decrease your rpm's by 200, decrease one inch of pitch and increase rpm's by 200. These are approximate but pretty close.

 

[Frank Acampora]

Re: help with prop

You don't have a lot of choices as far as props. In the catalogs I usually only see one small section for Force and there are 4 props 13X 15, 17, 19, and 21. You can try the 15 pitch and your RPM will rise about 200-400. Speed may stay the same or may go down slightly but acceleration will be better.

Now, That said, I also noticed in the Michigan prop ( I forget--it might be Vortex line) in the prop catalog the number is exactly the same for the force props and some of the Honda props. Might be able to do a little crossing there.

 

[jnk111]

Re: help with prop

Thanks for the info. Am I ok in the range I am now? Or is there something else I should be looking at?
I have changed fuel pump, made sure the throttle is opening all the way, looked at timing.


Thanks

 

[darrklim2]

Re: help with prop

Thanks for the info. Am I ok in the range I am now? Or is there something else I should be looking at?
I have changed fuel pump, made sure the throttle is opening all the way, looked at timing.


Thanks

If your sure your engine is running optimally and in the optimal position, then I would recommend going down in pitch to a 15. It is not good for your engine to be lugging along below the recommended rpm's. It is recommended that you shoot for the upper end of the recommended rpm range. In your case you want to be as close to 5500 as possible.