Proper Prop Size??

[OldPontooner]

I am new to this forum, and also first time boat owner at 76 years old. I have a 1988 20ft Lowe pontoon boat with a 1986 125hp force motor. My question is; What size, what pitch, and how many blades prop should be on this force motor?

Any and all advice is greatly appreciated.

Thanks in advance ~ Rick

 

[jerryjerry05]

Re: Proper Prop Size??

The proper prop will probably be around a 13/1/2 by 15p.
What's on there?
Being it a 20ft, it might be able to use a 17???
You need to go for a ride and check the rpm's at wot.
That motor should be running at about 53-5500
If the motors doing that and your prop is a 17.
Not running that? not reaching that? Then go down in size to a 15.
You should maybe post this in the prop section?

 

[Bifflefan]

Re: Proper Prop Size??

how many blades prop should be on this force motor?

Any and all advice is greatly appreciated.

Thanks in advance ~ Rick

I would go with a 4 blade. Top speed is not priority on a toon, and they give better lift, and slow speed handling than a 3 blade.
Again you will need to go by the rpm's you can attain. once you find the one that will let you run a WOT (wide open throttle) and not over rev, (with only you on board) then drop one pitch ie: if you hit 5500 rpm with a 3 blade 17p then go to a 4 blade 16p and you should be be right in there once you pile on the people.

 

[SkiDad]

Re: Proper Prop Size??

i second the 15 pitch - you can get the Michigan Match part number 072055.

 

[Frank Acampora]

Re: Proper Prop Size??

Does the engine already have a prop on it or do you need to buy one?

Last year I mounted a 125 on a 20 foot pontoon and the three blade 13 X 17 pitch standard prop worked very well. We achieved well over 20 MPH with it.

If your engine already has a 13 X 17 prop leave it. If you need to buy a prop, try a 4 blade 13 X 15.

Of course, this is all dependent upon having a tachometer. ANY prop you use would need to let the engine rev up to about the 4500-5500 RPM range at full throttle.

 

[SkiDad]

Re: Proper Prop Size??

Frank, have you found any 4 blade props that will fit the older Force 125 engines ?

 

[Frank Acampora]

Re: Proper Prop Size??

I have not really looked for one but If you look at props that will fit the small diameter gearcase Merc 90, they will also fit the Force.

Basically, you need to look at the prop sellers catalogs and compare everything. A lot of props with separate hubs for other engines will work on the Force--they just don't tell you that.

 

[jerryjerry05]

Re: Proper Prop Size??

There isin't a big market for Stainless props for the Force.
Try Michigan Propeller.
They'd have it if anyone did??