'94 Lowe 245 Pontoon with '93 85hp Yamaha..help with prop size

[HammondTiger]

I have a '94 Lowe 245 pontoon boat with a '93 85hp Yamaha. My WOT is about 6200rpm. My top speed is about 15mph. The prop is a 3 blade aluminum prop. The motor came off of a Skeeter bass boat and I am not sure of the size.
I'm pretty sure the pitch and diameter is not the best for a pontoon boat of this size. I'm just looking for a little more speed.
Any suggestions to help this boat/motor set up? Thanks!!

 

[steelespike]

Re: '94 Lowe 245 Pontoon with '93 85hp Yamaha..help with prop size

Your rpm is really screwy.You must have an amazing amount of slip.
Your prop numbers are probably under the prop nut.
Just guessing a 13" prop should be close to what you need.
Its better to be under propped because you can control the rpm if its too high.
If you end up over propped you shouldn't use the prop beyond high no wake speed.
I suspect your tach may be bad but we'll cross that bridge when we come to it.

 

[HammondTiger]

Re: '94 Lowe 245 Pontoon with '93 85hp Yamaha..help with prop size

Not sure what you mean by slip but im pretty sure my tach is working properly.
I'll check the size of the prop the next time i'm near the boat.
By 13" i assume you mean 13 pitch. What diameter is recommended and should i go 3 blade or 4?

 

[steelespike]

Re: '94 Lowe 245 Pontoon with '93 85hp Yamaha..help with prop size

Not sure what you mean by slip but im pretty sure my tach is working properly.
I'll check the size of the prop the next time i'm near the boat.


By 13" i assume you mean 13 pitch. What diameter is recommended and should i go 3 blade or 4?

All props slip a some on a typical runabout 6 to 12% would be usual. Actual speed compared to theoretic speed.
On a pontoon it would be higher;say about 20-25% Assuming it still has the skeeter prop at 17" pitch (just an arbitrary number)
your slip is about 69% Unless your tach is in error.We'll figure out the tach when we get a prop closer to the correct size.
When selecting a prop application; diameter is a secondary consideration. If a prop is intended for your motor and
application the diameter will follow. In the case of a pontoon if there is a diameter choice a larger diameter will usually do better.
If you look up prop pitches you'll note that generally as pitch goes up diameter goes down also usually a 4 blade may have reduced diameter. Usually a 4 blade will resist venting(losing grip) better than a 3 blade.
A 4 blade would be a good choice for a pontoon.