First ride on the superjet! BOOO

[GDFL]

Sounds like you might have different problems. My midshaft would spin, but it rattled around and let air in around it. A lot of air.

 

[Idok]

Waste can vouch for this. The first ride on my sj in my sig and it cavitated horribly. Ended up being a totally destroyed midshaft bearing. It was destroyed to the point that I found balls and pieces of the races in the hull. Needless to say it was sucking air like mad through the midshaft assy and did what you are describing. I doubt it's your problem, but it never hurts to check.
Garrett

i got 5 says thats what it is :cool2:

any takers???

 

[IceRocket1286]

lol. that might be it. for some reason, it had a bit of water in it when i pulled it on the trailer while it sat in the lake waitin for me, and I know i didnt sub it, I had no power to sub it. maybe it is that jewish midshaft. GREEEEEAT. hopefully its just the seal on it...

 

[IceRocket1286]

its got a solas YB65 prop, now what pitch is that? their site recommends a 14 17 for a 650, which is what the prop was originally used for. the 701 is recommended all of these!


CONCORDS
YB-CD-13/17*
YB-CD-14/18
YB-CD-15/19
YB-CD-16/20


X PROPS
YB-SC-X(15-18)
YB-SC-X0(15.5-18.5)*
YB-SC-XI(16-19)


IJK series
YB-SC-S(14-17)
YB-SC-I(14.5-18)*
YB-SC-J(14.7-18.5)
YB-SC- K(15-19)

 

[Marshj]

Dude. Its not the Pitch of your prop. get over that.

It'd run with that. You are sucking/creating air from somewhere

 

[jetskiking]

Definetly pulling air. Its not the pitch.

 

[cybermob2]

are you ABSOLUTELY SURE your engine is running right? is it nice and snappy?

if its "boggy" but still sounds like its revving to proper RPMs, its more than likely NOT.

either you are mistaking your engine for running good when its not, or you have a serious cavitation issue such as pump seal or midbearing. even with a diaper wrapped around the shaft you oughta be able to cruise, just cavitate when punching it.

 

[IceRocket1286]

HELLLOOOOO it cruises on plane and ONLY cavitates when i punch it, thats what im saying! and im sure the motor runs fine, it is nice and snappy like it should be

 

[Mile9c1]

This is easy to fix, you just have to spend a few hours going over your ski. First inspect the impeller/stator vanes because it's a 20 minute job to pull the pump. When you put it back on, put some silicone sealant on the pump seal just to make sure it's sealed (I never use it on Yamaha's, but it won't hurt). Let it dry before you go back in the water.

Make sure your pump shaft spins nicely freely while it's out.

Last think check the midhsaft bearing. You'll have to slide the engine foreward to check it. It should turn nice and smooth.

 

[IceRocket1286]

This is easy to fix, you just have to spend a few hours going over your ski. First inspect the impeller/stator vanes because it's a 20 minute job to pull the pump. When you put it back on, put some silicone sealant on the pump seal just to make sure it's sealed (I never use it on Yamaha's, but it won't hurt). Let it dry before you go back in the water.

Make sure your pump shaft spins nicely freely while it's out.

Last think check the midhsaft bearing. You'll have to slide the engine foreward to check it. It should turn nice and smooth.

I checked it and it spun fine. the pmp has been off since..... saturday night and it is fine, stator veins and seal are perfect.

 

[Mouthfulloflake]

so.... the pump seal is good, the impeller to housing clearance is within spec, the engine is running good....

But it cavitates really badly when you gas it?

must be cursed.

 

[CarterB]

check your intake duct...its the black plastic peice that goes before the imppeller housing.....rocks can take chunks out of it and will cavitate proportionately to the ammount of damage there is to it. i just fuct mine up the other day to the point it would idle but any more throttle than that and itd go full rev and no increase in propulsion. $61 part

 

[h2odesperado]

^^ pump shoe?

 

[IceRocket1286]

the pump shoe is fine. i talked to a guy who races superjets still in our region, a friend of mine. Hes an SJ die hard, said the 16.5 pitch of the prop might have worked on the stock 650, but he said for sure the 701 with the dry pipe is just spinning it like mad.

he's gonna give me a few props to try out that he has layin around

 

[Mile9c1]

The stock pitch for the 650 Superjet and the 701 Superjet is almost the same (if not the same). You'd need a ton of power to make it spin for no reason.

Do you have a ported cylinder?

 

[IceRocket1286]

yes, the stock pitch is the dang close, but the 701 with a drypipe has more power, especially with the pipe. no porting at all. m buddy who is letting me test some props said hes had the problem and its too much for the prop

 

[romack991]

yes, the stock pitch is the dang close, but the 701 with a drypipe has more power, especially with the pipe. no porting at all. m buddy who is letting me test some props said hes had the problem and its too much for the prop

but what ur saying doesnt make sense to me.

you stated it barely gets on plane. unless this was doing this with the 650, something else is up.

if you are slowly increasing rpm, the 701 should act and go the same as the 650. think about it, if rpm and acceleration are the same, the prop should work exactly like it did with the 650. the only reason why you'd see cavitation differences is when you hammer the throttle, the 701 has more power so you have more accleration, prop cant keep enough pressure so it cavitates.

 

[jetskiking]

yes, the stock pitch is the dang close, but the 701 with a drypipe has more power, especially with the pipe. no porting at all. m buddy who is letting me test some props said hes had the problem and its too much for the prop

Heres the thing about what your saying. A motor only has as much power as you give it with the throttle. Yes power could cause cavitation but only if you nail it and only for a second. It should still get up on plane. If what your saying your symptoms are is true and you cant get on plane even when gradually giving gas then I promise you its not the pitch of the impeller. What do you have done to your pump? Wetwolf cone? Bored nozzle? If your confident its running O.K. the impeller isnt beat up and everything else is in spec, I'm baffled somethings not right and its not the pitch.

 

[jetskiking]

Haha we were typing the same thing at the same time:wink:

 

[romack991]

Haha we were typing the same thing at the same time:wink:

lol, sure we were... copycat :wink:


i think you put a trim on there, check the size of the reduction nozzle to the stock, also if you put a shorty cone on it. both those could affect it. did you silicone your intermediate shaft when you installed it?