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90hp what prop

BulldogsCadillac

BulldogsCadillac

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Hey guys, I have a 2075 GLi with 2 25" toons, a 90hp Yamaha 4stroke, right now it has an aluminum 13 5/8 13k prop that the dealer had installed. I currently max out at 22 GPS'd and get no increase from about 5300 rpm's and up. I don't really want to go stainless due to cost and from what I've read on here and around the biggest benefit of SS is with the higher horsepower motors. But I am in a bit of a pickle, we go tubing and kneeboarding so want to keep some "holeshot" but would like a decent topend too. Am I pretty much at the right setup, or does someone have better? Thanks for the help!

Derrick
 
I have a 75hp 4 stroke with a 13 pitch prop I can also get 22 to 24 top end speed you should check out a 15 pitch prop, you will lose a little hole shot but gain a couple of mph some where around 24 to 26 with a pontoon a hole shot is not as important than with a ski boat or bass boat, I just sold a 20' bass boat with a 24 pitch prop took it about 8 seconds at full throttle to come out of the water but when it did it would run around 80mph this was with a 225 2 stroke

I would go up in pitch if you want more speed, some dealers and marinas have used prop you can try out, this is a good way to see what you are happy with.
 
Try a mercury 14x10p or 14x11p.

Just so you know though...

You're not going to do better than maybe 25mph with that boat/engine combo. 23mph is pretty much right on the money for what you have. If you're only hitting 23, then you MAY have another mph or so to wring out.
 
Thanks for the replies, I just wondered since it tops out well before rev limiter that maybe a different prop might give it that extra oomph! Haha that and people with smaller engines saying that they are getting basically the same with smaller motors, just wondered if I'm doing something wrong!
 
Your pretty much hitting the limit of your toon by design. Longer toons may be able to go slightly faster with the same Hp.
 
Maybe you guys could advise me I just bought a 257L 2003 with an 80 yamaha 4 stroke with a 14" with a 11 pitch I have a little vibration at full speed the prop has some rough spots on it that I think thats causing the vibration. Going to replace but just wondering what you guys thought a good prop pitch for 25 foot toons would be. And where to get it.

Thanks Darryl
 
Those specs should actually be pretty good for a 90.
 
BulldogsCadillac said:
Hey guys, I have a 2075 GLi with 2 25" toons, a 90hp Yamaha 4stroke, right now it has an aluminum 13 5/8 13k prop that the dealer had installed. I currently max out at 22 GPS'd and get no increase from about 5300 rpm's and up. I don't really want to go stainless due to cost and from what I've read on here and around the biggest benefit of SS is with the higher horsepower motors. But I am in a bit of a pickle, we go tubing and kneeboarding so want to keep some "holeshot" but would like a decent topend too. Am I pretty much at the right setup, or does someone have better? Thanks for the help!

Derrick
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I have the exact same model and motor as yourself. My dealer installed a 15 inch prop. The GPS speed was 25.5 mph at 5800 rpm WOT. I wanted to increase the RPM closer to 6200 so I purchased a 13 inch prop. Results were, less speed, aprox 21 mph, no noticeable effect from 5300 to top RPM, which over revved and seemed to cavitate. Not a good choice, so back with the 15 inch. The power with the 15in. is more noticeable throughout the range right up to WOT. No dead last portion throttle. On Shuswap Lk, elevation is aprox 1200'. You may want to try a 15in. Good luck.
 
yyj200 said:
I have the exact same model and motor as yourself. My dealer installed a 15 inch prop. The GPS speed was 25.5 mph at 5800 rpm WOT. I wanted to increase the RPM closer to 6200 so I purchased a 13 inch prop. Results were, less speed, aprox 21 mph, no noticeable effect from 5300 to top RPM, which over revved and seemed to cavitate. Not a good choice, so back with the 15 inch. The power with the 15in. is more noticeable throughout the range right up to WOT. No dead last portion throttle. On Shuswap Lk, elevation is aprox 1200'. You may want to try a 15in. Good luck.
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Thanks for the reply, this whole prop decision was too much for me, so I bought a new boat. Haha seriously though, thanks for the recommendations, I think you are probably right on choice of prop, if I find out who the dealer sold my old boat to I will mention it if I see him around. Hopefully going this weekend to pick up the new unit!

Derrick
 
BulldogsCadillac said:
Thanks for the reply, this whole prop decision was too much for me, so I bought a new boat. Haha seriously though, thanks for the recommendations, I think you are probably right on choice of prop, if I find out who the dealer sold my old boat to I will mention it if I see him around. Hopefully going this weekend to pick up the new unit!

Derrick
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Great. Hope you enjoy your new boat. Weather is finally getting hotter here now too. Time to get out. Good luck with your new acquisition.
 
Hello all! I just bought a new 2012 22SSLX w/ 90 4stroke Merc. What kind of top end should I expect and will this be good for pulling kids (12yrs old) on tubes? I come from power boats, so don't really know what to expect!

Thanks in advance for your comments!
 
Hey Bluegrass, based on my experience and the posts above yours, probably between 21-25 mph. Depending on prop and toon size as well.
 
I have a 22 SLX with a Yamaha 90 and 25" pontoons and have been curious about changing from the stock prop of 14. Not sure of speed, could check with our tom-tom GPS, but I am maxing out 5100 RPM. Could a combination of a 15 prop along with a hydra foil attachment bring a more balanced of increased speed and hole shot for towing inflatables? Or is the hydra foil not very effective at these top speeds?
 
If you want to get the rpms up, which you should, you need to drop to a 13 pitch.
 
I did get more information on performance last weekend 8/25. 13 7/8 x 15 aluminium prop, if memory correct, and got just above 5100 rpm and hit 24 mph per our GPS. This seems to be the norm among other owners information posted around the forum for a Yamaha 90 4 stroke. This is with 2 souls on board, nearly full tank of gas and cooler. Water was a bit choppy and trim seemed to be best at almost mid way. The mph is about what I was told is about where this boat should be. I am also running 93 octane fuel to max out the power to get the most from the 90 horses.

Just beginning to get some understanding of prop pitch effect on RPM and MPH. Thanks for the input.
 
You should be at or around 6000 rpms @ WOT. I suggest you try a 13p prop with a little more diameter.
 
Also, if you're running 93 octane on a 90, you best be adding some Ring Free to the fuel as you will be getting carboned up. The motor isn't designed to run on that high of an octane. They recommend 87, if you are doing the 93 to avoid ethanol that's fine,just run the ring free. Or you can just buy 87 octane and add fuel stabilizer and conditioner and save yourself some cash. I doubt there will be any real performance gains. Just my thoughts.
 
Drop the pitch like Carl said. Definately try to get up to the 6000 rpm motor limit (I assume that is your motor limit) without pulling a tube, as when you DO pull a tube your top rpm will sink very fast.

Also, I can't help but recommend the Spitfire. I had a 115, and the Spitfire made a big difference pulling a tube. I lost about 3 mph top speed, but I gained about 3 mph while pulling a tube. They are not apples to apples.

Correlating top speed performance with tube pulling performance is not the way to look at this. When you are pulling a tube with a small engine, you want torq, not top speed.

Take an old 10-speed bike for example. Would you use your fastest speed in 10th gear as in indicator of how easy it would be to pedal up a steep hill in 1st gear? That's what you're doing when you try to use top speed as a proxy for tube pulling performance.

Get the smaller pitch. Get the rpms up. Get a Spitfire if you have the means.

Then get a 150 like I did and sell the Spitfire on ebay. Ha ha ha. Seriously though, if you want to maximize what you have for tube pulling, go down in pitch to get more torque, don't worry about top speed so much.
 
By the way, I had a 15p Black Max on my 115 at first, then I bought a 13p Spitfire for exactly the same reasons you mention. You can search back though some of my posts on this over the last couple months. I was asking the same questions you are, and got a lot of help on this from forum members.
 
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2014 20slx with 90hp mercury,25"tubes with 13.8x13 4blade prop.Dealer said he installs this setup on toons most often.It seems to pull steady up to 6000 rpm.We do not tow but cruise the intercoastal n&s of fort Desoto.
 
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