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21slx prop suggestion

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Kane

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Hey guy,

Im new to pontoons... I just traded my Crownline in for a 2015 Bennington 21slx tri toon with a Yamaha 115 4 stroke. So far Im loving it with no regrets. I was ready to make the change.

Only thing wrong is Im not sure this motor is proped right. Im not sure whats on it as I type this. I assume its stamped on the prop and Ill check it out tomorrow but its clearly not a pontoon prop. I ran the GPS today and was only getting 22mph. that seems way low. Ive seen reports of the setup getting 30 to 35 mph.

any prop suggestions.
 
I purchased the yamaha stainless pontoon prop 14" 13p for a 22 slx with yammi 115 4 stroke. I can get 34 on gps with 2 persons aboard with the bimini open! If I have 4 people it drops to around 30 if everyone is in the back seats. Did get 36 one day 1 person & dog .bimini closed. I have 2- 25" tubes w/ lifting strakes.
 
Kane said:
Hey guy,

Im new to pontoons... I just traded my Crownline in for a 2015 Bennington 21slx tri toon with a Yamaha 115 4 stroke. So far Im loving it with no regrets. I was ready to make the change.

Only thing wrong is Im not sure this motor is proped right. Im not sure whats on it as I type this. I assume its stamped on the prop and Ill check it out tomorrow but its clearly not a pontoon prop. I ran the GPS today and was only getting 22mph. that seems way low. Ive seen reports of the setup getting 30 to 35 mph.

any prop suggestions.
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We need to know what hull you have first, and if you have strakes and how many.
 
I have the express performance package tri toon. Im not sure how many strakes
 
Does the boat sit in the water or out when you are not using it?  Scum can cut speed in half.

What are the engine RPMs at WOT?

You should look to see if it has strakes on the inside, outside or both sides of the outer toons (Express will have strakes on both sides of the center toon) and check your prop pitch and diameter next time you are at your boat.

Without all of this info, it is difficult at best for the guys here to help you.
 
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I was out today. The outer toons have no strakes. The middle toon does have strakes. The boat is brand new with 7 hours on it so no scum on the pontoons.  The prop they put on this is a 13 5/8 - 14 k

 with 4 adults in the boat. Trimmed all the way down Im throwing 6150 rpms and 21-22 mph. trimmed to about half way up on the trim indicator the rpms were about 6200-6250 and we hit about 27 mph
 
Kane said:
Hey guy,

Im new to pontoons... I just traded my Crownline in for a 2015 Bennington 21slx tri toon with a Yamaha 115 4 stroke. So far Im loving it with no regrets. I was ready to make the change.

Only thing wrong is Im not sure this motor is proped right. Im not sure whats on it as I type this. I assume its stamped on the prop and Ill check it out tomorrow but its clearly not a pontoon prop. I ran the GPS today and was only getting 22mph. that seems way low. Ive seen reports of the setup getting 30 to 35 mph.

any prop suggestions.
Click to expand...
For comparison, our 21SLX twin-toon, no strakes, 90HP Yamaha runs 21.8 MPH on the GPS, RPM maxs out at 5300-5500.  Don't know which prop I have though.
 
Kane said:
I was out today. The outer toons have no strakes. The middle toon does have strakes. The boat is brand new with 7 hours on it so no scum on the pontoons.  The prop they put on this is a 13 5/8 - 14 k

 with 4 adults in the boat. Trimmed all the way down Im throwing 6150 rpms and 21-22 mph. trimmed to about half way up on the trim indicator the rpms were about 6200-6250 and we hit about 27 mph
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I would say you are pretty close to dialed in.  Changing the prop likely will make your max speed worse.  If you insist though, I'd try a 15p, but I wouldn't bet anything that would help you.  It will make acceleration worse for you for sure, and it's only a flip of the coin (in my opinion) whether it will improve your top speed.  I had a 115, and even with 6 strakes, I'd bog down quickly with extra passengers.  Trimming the trim setting makes a big difference.
 
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I have a 15 21slx tri toon with same Yamaha 115. My prop is a Yamaha aluminum 13.25x17p. I run 5900 at 34-35 mph. So your are propped wrong.
 
Rule of thumb is 200 rpm per inch of pitch.  If you go from a 14 to a 17, that will drop ~600 rpms.  Not sure I'd want to run it that low, but I don't know what the WOT range is for that motor.  5600 seems low, which could lead to bogging down the motor.  My old Merc 115 ran 6400 rpms, and I think that was at the top of the range.

BUT you did say you had 4 people on board when you were running 6200 rpms.  Do you hit the rev limiter when you are out by yourself?
 
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But I have same set up with 17 p and I got 5900 with top rpm recommended at 6000-6100 so it works well for me
 
I havent had the boat out alone yet to see if I hit rev limiter.  Owners manual says full throttle RPM range for this motor is 5300 to 6300 so Im just about at the top with 4 adults.
 
Sounds like the wrong prop or the motor is mounted too low. You're not doing bad, but can do much better. Just remember not to exceed top rpm at WOT.
 
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