proper prop sizing and pitch for max speed

[dsiegrist91]

I am wondering if anyone can tell me the right size and pitch prop I should be running on my 87 force 125 long drive. I am running it on a 1992 Spectrum fish and ski. The weight of the boat is 1045lb without equipment and is 17.5 ft long. it is aluminum deep v haul. The motor is rated for 5500rpm the problem im having is finding a tach for it. thank you

 

[jerryjerry05]

You should need a 17 or 19p

BUT!!! without a tach you'll just be guessing just like I am

You need a 20 pole tach.
Try Faria, Teleflex and google.

Michigan Propeller has a prop finder service.
Send them the info and they can give you the size for your boat.

My boat/motor setup called for a 17p
I wanted a bit more speed so I went t a 19p
I got more!! About 2-3 mph faster and the fuel usage went up about 15-20%
So make sure you get the right one.

 

[Redbarron%%]

If you have a problem finding a 20 pole tach you can use an inductive tach that has a wire that wraps around a spark plug wire.
They are available from $15 or so. Some less.

 

[SkiDad]

i would go 17 pitch michigan prop - when they put 19's on these boats it was a bad idea b/c of the low gear reduction in the 125's. a 17 will put you about 40 mph and around 5000 rpm

 

[jerryjerry05]

Don't buy something without really knowing what's needed?
The 17ft. Bayliner with a 85hp used a 17p.
This boat's lighter and has 40 more hp.
He could actually need a 19p maybe even a 21p ??

With out testing he would be spending $ on something he doesn't need?

 

[Scott Danforth]

dsiegrist91 You NEED to know your RPMs at speed while loaded

You need to know your GPS speed

No way around it. We are just pulling guesses out our collective back sides without the info

Only with those two pieces of information and the other information that you posted can anyone offer a suggestion