Prop selection help

[3ric]

I have a new to me 2012 Lowe ss230 pontoon with a 2012 Mercury 115 four stroke on it. I am new to the world of prop selection. Now that I have done some trial and error, maybe you all can help me dial this in. The engine is rated for wot rpm at 5800-6200. The following tests were done with about 500-600 lbs of people and gear and half a tank of fuel. I would like to pull a tube/skis/kneeboard with this boat.

The prop that came on it is 13.75x15 and I’m getting 6150 rpm and about 25 mph at wot. It’s the one in the pic that has a couple bites taken out of it. I will replace with a new one. I also tried a 14x13p recommended by a random prop store getting 5800 and about 31 mph at wot, and a 13.25 x16p recommended by mercury’s prop selector website getting 5400 rpm and about 28 mph at wot.

Is the 13.75x 15 that was originally on it the right prop? Or might someone have a better recommendation?

 

[Scott Danforth]

Is the 13.75x 15 that was originally on it the right prop?

based on what you provided - yes

 

[jlh3rd]

I have an '06 Lowe 24' twin tube, 25" diameters, merc 115hp CT motor.
These are performance #'s for the props I've used/use.
My research says your boat is 24'....I don't know what diameter your toons are.
To answer your question, yes, that prop is where you need to be, especially if you want to pull more load. Stay with it.
You have already discovered that you can trade speed for rpms but can't have both. You also see that too much pitch (16p) lowers speed AND rpm. You'll need those higher rpm's when loaded down..(torque).
The # of blades makes a difference also.
I had to run the 3-16x12 to pull tubes with teenagers and people on the boat.

 

[jlh3rd]

I found that 2011 115 mercs WOT is 5800-6400....are you sure about yours?My 2021 is 5-6000 WOT.
Regardless, you're where you need to be.
I was a little surprised at the big difference with the 16p prop, but that's what you got.

 

[jimmbo]

The prop that came on it is 13.75x15 and I’m getting 6150 rpm and about 25 mph at wot. It’s the one in the pic that has a couple bites taken out of it. I will replace with a new one. I also tried a 14x13p recommended by a random prop store getting 5800 and about 31 mph at wot, and a 13.25 x16p recommended by mercury’s prop selector website getting 5400 rpm and about 28 mph at wot.

Those Numbers don't add up. A 15" turns 6150 rpm and gave 25mph. Then you say a 13" turned 5800 rpm and gave 31 mph. A lower Pitch Prop, spinning slower doesn't give higher Mph. Even the Numbers for the 16" don't follow the usual pattern.

 

[3ric]

I found that 2011 115 mercs WOT is 5800-6400....are you sure about yours?My 2021 is 5-6000 WOT.
Regardless, you're where you need to be.
I was a little surprised at the big difference with the 16p prop, but that's what you

 

[jlh3rd]

Maybe the 15" and 13" were mixed up in posting.....that would explain that not adding up....
we need accurate #'s for accurate opinions.