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Prop ventilating

Omike

Omike

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Inverness Fl
I have a 2015 21slx with a Yamaha 115b. Prop is 13.25x17 aluminum 3 blade. When I turn hard at speed it ventilates badly. Especially when pulling a towable or skier. My engine is mounted at the 2nd hole. I'm thinking if I drop the engine to the top hole it may help. Thoughts? And thanks in advance.
 
Do you have your outdrive trimmed up while turning hard?!?
 
Well it's defiantly worse when I do. Biggest thing I'm wondering with this being my first pontoon is, is this a characteristic of the sps or is there something else? I've always had v hulls and didn't notice this as much with those. I know trimming up will make it worse but I notice it with it trimmed down also.
 
Both w/the bowrider we used to own and our current boat we always keep the trim all the way down while tubing, skiing, wake boarding, or while making sharp turns and the prop won't cavitate.

Never had an outboard so I can't help you with what hole to mount your engine in. Hopefully somebody else will chime in........
 
I have an SPS with a 150 and I have to trim down while turning .
 
I trim down too coming into a hard turn. Haven't pulled a tube with this boat yet so I'll be curious to see how that goes.
 
I don't tow ,but I still have trim it down in turns .
 
I also have a 21slx. It has never ventilated the prop but my toon is a very different configuration. Regardless, I tend to agree with your original thought. Lowering the outboard is the most cost effective thing to try first and is what I would try.    
 
Sounds like it's mounted too high. Mine does it if I'm trimmed up when I turn hard but not if I trim down. I'm in the lowest position. 
 
I agree with Nick.  Sounds like it's mounted too high.  Mine will ventilate when turning hard tubing if not trimmed all the way down, but I have Express and I'm in the lowest position.

Not sure if lowering it is a DIY thing or not.  Could be.  Two bolts are in holes while the other two slide...  I wouldn't want to have move it up a hole though.
 
I think I'll stop by the dealer in the morning and ask them about moving it down a notch. If they won't I have a cherry picker that should work fine to do it myself.
 
Keep it trimmed down....  I have no problems with VERY sharp turns.... only trim up when looking for longer run at higher speed.... (22ssrx sps)
 
What kind of rpm's are you turning with a 17 pitch prop on 115 horsepower.  Your lower unit's gear ratio should be 2.15:1.

My F150 is only running a 15 pitch prop at 6000 rpm's, and I'm running a 2:0:1 gear ratio.  And it's substantially more motor than your 115 hp.

Your 17 pitch prop may not be allowing the water to stay on your propeller long enough--causing severe slip.

Dealers use an eye that screws into the top of the flywheel that their cherry pickers/hoists hook onto in order to install and adjust engine height.  Dropping the engine down would be a good place to start.

What does your dealer say?  To me, it's his responsibility to initially get your motor properly installed and propped to do the job you're asking of it.
 
I didn't even catch the part about it being a 17p prop. I ran an 11p on the F90 on the old boat. Tried a 13p and it was to much for it to spin. I'm at higher altitude than most of you, but still. Hard to imagine an F115 spinning a 17p. 
 
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My old 115 used a 15p.

What rpms are you seeing? This is a different issue altogether from your venting issue.
 
Guys I think the prop is fine at wot I'm running 5800-5900 rpm and about 35 mph. To me it seems about right.
 
That sounds right. Are you sure its a 17? The numbers don't add up.
 
Says it clear as day on the prop. And why are we up this early on a Saturday? Lol
 
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