25 hp prop question

[lundrebel]

I have a 1998 Johnson 25 hp with a standard 10x13 prop 3 blade. This was on when I bought the boat. I was wondering If I would gain anymore top end speed if I went to a standard 10x15 prop. Would this slow the engine rpms down to low? Just looking for 2-3 mph to finish planing out to boat with 2 people in it. I have a 1998 Lund Rebel fishing boat that is 16' long, tiller. I have a set of hydro fins on the motor already. I'm just looking for a couple mph on the top end. I have even tried premium gas but not much difference Any ideas would be great. THANKS

 

[steelespike]

Re: 25 hp prop question

You will likely get better results in the prop forum.
Premium gas is a waste on a motor intended for 87 like yours.
It will help if you read the stickies at the top of the prop forum page and the helps on the prop store page.
We need to know a whole lot more before making a prop change.
Is the boat a bare bones or loaded with a floor and livewells etc.
Is the motor a 2 or 3 cylinder?
We need the present max rpm and speed lightly loaded.A Tinytach will help with the rpm.
A gps for speed.Does the boat not plane with 2 aboard?
A "standard" prop implies came with the application on that boat.
Going to a 15 in this case is a change.
Without the rpm and speed you can't tell if you need to go up or down or how much.
The motor must operate within its rated rpm.Let us know what you find out.
Its ulikely you would go up in pitch.

 

[dew2]

Re: 25 hp prop question

I had a lund rebel 16 with a 35 evin on it.I had the same problem.What I found out is the foam flotation is sprayed directly to the aluminum hull under the floor,leaving no where for the water to drain. The foam was saturated with almost 280 lbs of water it is like a sponge.
Last fall I picked up a 14ft lund cheep. The one with the split 2nd seat and floor it had a rotted floor,removed the ply floor and it had the same problem 163 lbs water!! Poor design for what is supposedly a top of the line alum.boat.
I actually could take a handfull of the foam and squeeze it and that handfull would make a cup of water. Look at the specs of the boat for its weight then bring it into a scale.