Prop size for 75HP Force?

[dmlinal205]

I currently have a 1996 75HP Force on a 1992 Foxcraft that is 16ft. From what I have read the boat weighs around 900 #s. I have a 10" x 14 pitch aluminum prop on the boat right not and at 5800 RPM my max speed is 30 MPH. This is according to Humminbird GPS. From what I have seen on other threads others are getting up to 40 MPH on their bass boats with the same engine. Can anyone tell me if I have the wrong prop on, or if there is possibly other issues, or if you have the same engine and close to the same prop what you are using? The original prop the motor came with was much larger than a 10", possible a 14". I couldn't tell you the pitch or the make of the prop, I damaged it beyond repair and threw it out without realizing the valuable info on it. But, it would run about 36 MPH with two people in the boat.

Thanks for any input.
Mike

 

[monkey bizzness]

Re: Prop size for 75HP Force?

hey mike, i have a 16 ft bayliner capri, w/ a force 85 on mine and im running a 13" X 21p and i have a 19p for a back up. both are alum. if you have enough clearence i would go with the larger diamater. If you need a good prop call W&L Prop Repair in Moneta, Va. ph 540-297-8351. They CAN get whatever you may need. Hope this helps.

 

[Cannondale]

Re: Prop size for 75HP Force?

Well, here's a link to iboats' prop selection, from 8 to 17 pitch. But the diameters are 12" at the 8P to 10" at the 17P.
http://boatpropellers.iboats.com/Fo...id=160&**********=103942866&*******=871364612

Don't think you ever had a 14" diameter prop on that motor, at least not stock.

 

[Frank Acampora]

Re: Prop size for 75HP Force?

That engine is topping out at too high an RPM. If indeed you have a 14 pitch prop on it and if indeed it is turning 5800, you need to step up 2 pitches to drop it by 400 RPM. This should also improve top speed somewhat.

For your application, that engine uses a 10 inch diameter Mercury prop off a Merc 40-50 HP engine. That is, 10 inch diameter when used on planing hulls. The larger diameter, low pitched props are for pushing displacement hulls like pontoons. So, there are a lot of them out there. Before rushing out and buying a prop, see if you can't find someone near you willing to lend you a prop for test purposes

 

[jerryjerry05]

Re: Prop size for 75HP Force?

Go to the local dealer.Talk to the top mechanic.Lots of dealers have props they will loan you to make sure that you buy the right one.
Of course they want you to buy from them.Jerry

 

[steelespike]

Re: Prop size for 75HP Force?

It seems to me you are over propped yet your rpm is way high.
You should verify your tach. Borrow a shop tach or get someone to go with you to check.