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2008 Yamaha VX Sport - low on power

Jameson Clark

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Recently purchased a new to me 2008 VX Sport and double trailer to go with my 2007 VX Cruiser. Test drove it quickly after work and all seemed fine. After first trip out on the lake, it's obvious it is down on power. When accelerating to get on plane, it only gets to about 6000-6500 rpms and then slowly increases up to about 7000 but never gets to the 8000 rpms the other VX gets to. Speed is of course down, topping at 39-40mph. Went ahead and changed all the plugs as a first step and it didn't really change anything.

Not sure what to check next. It runs great, starts right up, idles smooth, and never gives any indications of running concerns other than the lack of power/rpms. Any ideas from the experts here?? Thanks!
 

Jameson Clark

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The VX line are used for rentals great ski reliable, but not rocket ships 40 to 50 is about right 110 hp its all it got
I'm not too worried about speed. But it is noticeably down on power compared to the other VX I have. 6000 rpms out of the hole takes some time to get it on plane! The other goes straight to 8000 and gets on plane well enough to pull up a 200lb skier. It also tops out about 47mph.
 

Scottintexas

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will it rev on the hose immediately to 8k or do you see the same scenario ?

if it rpm's good on the hose then you can narrow down to impeller/pump issue

maybe your impeller is dinged up
maybe you have an air leak causing cavitation (what does the silicone look like that holds the intake grate and housing on look like?, pull on it with your fingers as it may look good but have no adhesion and when the pump starts sucking it pull the silicone away from the metal)

good thing is you've got a known tester available,
I think I might swap impellers between the skis to see if the problem moves from ski to ski or persists,


.
 

Jameson Clark

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Revs fast to 8000 under no load. We had impeller issues on the other last year and it would cavitate terribly when getting on plane. This one does not cavitate, just has no power under a load.

Swapping impellers is still a good idea that I can try!
 

1WetBoat

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I don't recall but I think that model has a learner keyfob that limits speed and rpm's. If it has one, verify which one you have. There might also be a mode button on the dash that lets you select learner mode. Honestly don't recall which year had one or the other but that is what it sounds like to me.
 

Betik

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I don't recall but I think that model has a learner keyfob that limits speed and rpm's. If it has one, verify which one you have. There might also be a mode button on the dash that lets you select learner mode. Honestly don't recall which year had one or the other but that is what it sounds like to me.
If that is the case that will be hilarious
 

Jameson Clark

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I don't recall but I think that model has a learner keyfob that limits speed and rpm's. If it has one, verify which one you have. There might also be a mode button on the dash that lets you select learner mode. Honestly don't recall which year had one or the other but that is what it sounds like to me.
Nope. The sport model doesn't have that option. Our VX Cruiser does, but there is an obvious light that comes on in the display to tell you.
 

1WetBoat

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Nope. The sport model doesn't have that option. Our VX Cruiser does, but there is an obvious light that comes on in the display to tell you.
Ah, ok. Wasn't 100% sure, thanks for the info.
 
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