25 Yamaha prop pitch change How much?

[over60pirate]

I have an old 14' fg runabout with a 25 yamaha 2 stroke.
With full load, the boat tops out at 28 mph. No tach, but my ears say the rpm is at or near the max. I back off and cruise at about 24mph. The motor has no problem getting up to wot and speed. Hole shot is decent also.
I would like to raise my cruise speed.
The prop is a 9 7/8 x 9 pitch.
I was thinking of 1 or 2 more on the pitch, but don't want to go too far.
Any idea on this?

 

[choppywaters]

Re: 25 Yamaha prop pitch change How much?

I have an old 14' fg runabout with a 25 yamaha 2 stroke.
With full load, the boat tops out at 28 mph. No tach, but my ears say the rpm is at or near the max. I back off and cruise at about 24mph. The motor has no problem getting up to wot and speed. Hole shot is decent also.
I would like to raise my cruise speed.
The prop is a 9 7/8 x 9 pitch.
I was thinking of 1 or 2 more on the pitch, but don't want to go too far.
Any idea on this?

Ive been researching props. etc. as I am trying to figure out some things on my boat. The more pitch you have or go up will reduce your rpm's by a couple hundred. If your happy with most of the performance I would go up by 1.

 

[connemaraisland]

Re: 25 Yamaha prop pitch change How much?

I don't have my prop Yamaha book here but if my memory is correct the prop you have on your engine is the correct pitch for a Yamaha 9.9 two stroke - no wonder it is good out of the hole! Best way to get the correct prop is to look at a Yamaha online parts listing and it will give you the std one shipped with the motor. BTW 25hp is the highest Yamaha engine that comes with a prop, bigger HP is additional cost - Bob

 

[steelespike]

Re: 25 Yamaha prop pitch change How much?

If prop pitch is right And speed is by gps it appears your turning 6700.
It would be much better to have a tach reading both now and after your prop change.
It appears A 3" pitch increase would put you around 6000.
A 12" prop at 6000 rpm could net about 33 mph.It will slow your hole shot.
It will be harder to push a load.