115HP Yamaha SHO Prop Pitch?

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gotnitro

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Hello all,

New to the forum and new to owning a 2021 Bennington 21ft SLX (performance package 3rd toon) with what I believe is a 13.5- 17P prop. It appears to be the standard Yamaha aluminum white anodized 17P prop they use for these engines. (not new to driving all my drunk friends boats back to the docks, been sober for 15 years)

She gets up and goes, spools right up to 6300-6400RPM (with that Yamaha 115HP SHO) almost instantly. It goes about 32-33 with my wife and I on it.

My question for the pros: Would going to a 19P prop with the same diameter give me more top speed? Reason I ask is because of how easily it spools up to its MAX RPM currently, I almost feel like there is more room to go. I guess the only real way to know is to change the prop and find out myself, I figured I'd ask in here first. Thanks for reading and thanks in advance for your replies.
 
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According to the Bennington build site a 150 is the max


Yes, you are correct. It's been 6 months since we sat down to build this.

Back when we built it the cost difference between a 115 SHO and a 150 for the MPH we got didn't make much sense. That coupled with the power steering was several thousands more. I'm just trying to get a few more MPH out of this 115 mill if its possible. I also figure I wont have to run it at such a high RPM either and will get better fuel "mileage"..

EDIT: Edited OP.
 
If you have the standard 2.15 gear ratio for that SHO, your current prop is not the best choice as your calculated slip is 30+%. The upshot of that is you get mislead on what prop your combo should be running (The standard Yamaha 3-blade AL prop is not a great pontoon prop). In other words, I'd suggest you not waste your money on any 19p prop. IF you decide to go on a prop chase, a good pontoon rated prop for your combo will have LESS pitch because slippage will go way down, but hookup will be better across the RPM range. Expect a good choice for your pontoon to be something not more than 15p (and likely less...maybe like a 13 or 14, depending on the specific prop). A prop that is a better match might offer a little more speed, but don't expect too much....
 

Not a VF motor but should be a close comparo - 35mph in the performance bulletin.

I was thinking the same as Party Barge, with pontoons since there is so much drag/wetted surface you need MORE diameter or else your slip% goes way up. Think of it this way - if you have too little tire contact patch on a Corvette, you'll easily bounce off the rev limiter but the work is just wheel spin, not forward movement. Same with props - there are a ton of considerations beyond just pitch, and even diameter (material, rake, barrel length, number of blades, blade area/shape, etc) that influence performance. You achieved max RPM and some good top speed, but what about your numbers across the RPM range? What are your fuel efficiency numbers? That data will also help determine how well the current prop is matched.

I would first find a prop meant for a pontoon or heavier boats - prop selectors are great for this. Also a search in this forum might yield a previous thread that can give some test data. Second, check OEM performance bulletins such as the link above. Lastly some prop swapping and testing is to be expected if you want to find that last 10% of performance since everyone's boat, boating conditions and performance objectives are different. I may want top speed, but you may want to whip around tubers.

You seem to have a good gut feeling for what you need, so keep asking the questions, do the research and try a few different props. Good luck!
 
If you have the standard 2.15 gear ratio for that SHO, your current prop is not the best choice as your calculated slip is 30+%. The upshot of that is you get mislead on what prop your combo should be running (The standard Yamaha 3-blade AL prop is not a great pontoon prop). In other words, I'd suggest you not waste your money on any 19p prop. IF you decide to go on a prop chase, a good pontoon rated prop for your combo will have LESS pitch because slippage will go way down, but hookup will be better across the RPM range. Expect a good choice for your pontoon to be something not more than 15p (and likely less...maybe like a 13 or 14, depending on the specific prop). A prop that is a better match might offer a little more speed, but don't expect too much....


Not a VF motor but should be a close comparo - 35mph in the performance bulletin.

I was thinking the same as Party Barge, with pontoons since there is so much drag/wetted surface you need MORE diameter or else your slip% goes way up. Think of it this way - if you have too little tire contact patch on a Corvette, you'll easily bounce off the rev limiter but the work is just wheel spin, not forward movement. Same with props - there are a ton of considerations beyond just pitch, and even diameter (material, rake, barrel length, number of blades, blade area/shape, etc) that influence performance. You achieved max RPM and some good top speed, but what about your numbers across the RPM range? What are your fuel efficiency numbers? That data will also help determine how well the current prop is matched.

I would first find a prop meant for a pontoon or heavier boats - prop selectors are great for this. Also a search in this forum might yield a previous thread that can give some test data. Second, check OEM performance bulletins such as the link above. Lastly some prop swapping and testing is to be expected if you want to find that last 10% of performance since everyone's boat, boating conditions and performance objectives are different. I may want top speed, but you may want to whip around tubers.

You seem to have a good gut feeling for what you need, so keep asking the questions, do the research and try a few different props. Good luck!

Gentlemen, thank you!

I called up both Bennington and Yamaha and both recommended MAR-PNTN3-V4-13 for my application. I still need to see what's on it currently, I'll get that tonight. Thank you again.
 
So just to update my thread. I was way off :rolleyes:

Turns out the prop that was installed from the dealer was an aluminum Yamaha 13.5D x 12P, exact GPS speed was 31.9 taken yesterday with my wife and I on (had a 1/2 full 90QT Cordova cooler and 40lb sub onboard too). Hope this new one I ordered Stainless 14D x 13P tested on a regular Yamaha 115 @ 35MPH and not a SHO will do the 35-36 MPH trick. :cool:
 
Just some info..Just went thru this with my 24 ssrx twin toons with a 90 Yamaha...trying to get anything more out of it on the top end. My results with 3 props where
Solas 14x11 22 mph 6100 rpm WOT
Turning Point 14X13 21.9 mph 5800 rpm WOT
Turning Point 13.75X15 23 mph 5100 rpm WOT
all tested 2-3 people full tank of gas
hope this helps..
 
Ahhh...your numbers are reasonable now. Stepping up to a more sophisticated and expensive prop should be an improvement.
 
According to the Bennington build site a 150 is the max


So because I bought this in DEC and basically just got it last month I forgot what I bought..

Mine is a 21 SLX with the performance package, center toon only goes back 3/4 of the way. MAX HP is 115 and its on the sticker. Could I go with a 150, sure.. Don't want to have the CG or County cops on my butt though.. When I built this, doing the performance package and not the SPS was THOUSANDS less considering I would have gone with a 150 SHO.

Just to update this on this boat for anyone looking for prop speeds.

Yamaha 13.5x12 went about 31, recalibrated all GPS and Tach 6200RPM
Merc 14x13 went 31.8 with the wind 6000 RPM
Yamaha 13.5x14 goes 33.4 about 5800 RPM

I lost all hole shot on that last prop, its a dog now in comparison. I have a Yamaha 13.5x13 on order.. When will my prop chasing end? Who knows...
 
So because I bought this in DEC and basically just got it last month I forgot what I bought..

Mine is a 21 SLX with the performance package, center toon only goes back 3/4 of the way. MAX HP is 115 and its on the sticker. Could I go with a 150, sure.. Don't want to have the CG or County cops on my butt though.. When I built this, doing the performance package and not the SPS was THOUSANDS less considering I would have gone with a 150 SHO.

Just to update this on this boat for anyone looking for prop speeds.

Yamaha 13.5x12 went about 31, recalibrated all GPS and Tach 6200RPM
Merc 14x13 went 31.8 with the wind 6000 RPM
Yamaha 13.5x14 goes 33.4 about 5800 RPM

I lost all hole shot on that last prop, its a dog now in comparison. I have a Yamaha 13.5x13 on order.. When will my prop chasing end? Who knows...
It shouldn't end until you've achieved your objectives. Some people accept mediocrity and subject themselves to hundreds of hours of inferior performance. It's like dating lots of women before you pick one to spend the rest of your life with - better get it right!
 
It's like dating lots of women before you pick one to spend the rest of your life with - better get it right!
And after being struck with a rock it can be left on the bottom of the lake. Hmmmmmm

OK, maybe a little too dark of humor for a Sunday morning!
 
And after being struck with a rock it can be left on the bottom of the lake. Hmmmmmm

OK, maybe a little too dark of humor for a Sunday morning!
And watch out for those models that don't have quality components, like plastic headlights! They might look good fresh off the showroom but over time may not age well!
 
Another update..

Put the Yamaha 13 5/8 x 13 on and top speed with only myself on and 1/4 tank was 35.7 no wind... Full tank (another 150lbs of fuel) and 2 people on board she goes 34.3.. I think I'm done lol... I have a few different props to choose from now if one should become scrap.:cool:
 
Another update..

Put the Yamaha 13 5/8 x 13 on and top speed with only myself on and 1/4 tank was 35.7 no wind... Full tank (another 150lbs of fuel) and 2 people on board she goes 34.3.. I think I'm done lol... I have a few different props to choose from now if one should become scrap.:cool:
Awesome! Glad to hear it.
 
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