WTF ! Does my ski have Herpes or something? What could be wrong?

[TexasTexas95]

Ok, so maybe its not herpes. I ruled that out I think. Seriously though, I am trying to diagnose the problem I am having with my old school superjet.

Memorial day weekend my ski was cavitating to the point that it was just pulling me around barely. Not enough speed to get me up and the speed never changed much even at WOT.
I pulled the pump and found out my pump seal was shot. I thought this was the sole cause of my problem along with a few small dings in my stock impeller. There still might be more to the problem though...

I was informed by though that ya, those things would cause me to cavitate but not to the point of almost going nowhere at wide open throttle.

I didnt hear any unnatural sounds except for one time before I installed the motor and turned the coupler by hand i heard a single "ting ting" noise while I turned the impeller. It sounded like someone dropped a pebble or two on a blade of the impeller. It was just once and I could not replicate the sound. (Just stating that so we can draw a diagnosis here)

The splines look excellent on my impeller shaft and I also took a flashlight and looked into the splines up in the midshaft area. Those also appear to be solid and free from any metal bits. There are also no missing, chipped or dented teeth. This is harder to tell looking into the midshaft cause I cant feel them by hand. They look solid though.

The big question is whether or not I need to put on the new pump seal and see if that solves my problem. Or, should I go on ahead and replace some other potential problems while I have the whole ass end off my ski. I really only wanna do this once.

 

[227]

From your explanation it sounds like its your pump seal. Replace it, they're cheap ($20) and its fairly easy.

 

[SUPERTUNE]

Make sure your mid shaft housing is not worn out or damaged and letting air down the pump shaft tube.
When you do put in the new pump seal...check to make sure your pump plastic shoe is not cracked. (very common)

 

[TexasTexas95]

Plastic pump shoe is not cracked and its sealed up good. I looked down the shaft tube with a flash light and all the splines look solid. I just wish I could get a closer look at them...Like I said before, there were no metal shards or bits and the end of the shaft where it connects to the midshaft has some grease on it. Is there something thats supposed to be in the midshaft housing around the shaft that will keep out air that I dont know about? I will post up the pics of what I have so far.

Pump seal exactly as it came from my ski...

Damage to the stock impeller. This is the worst blade, all the others have alot less damage...

This is a pic up into the midshaft. I know its hard to see, but the splines appear to be in good condition...

When I had the motor out, everything turned smoothly and if I grabbed the coupler in my hull, there was no play in the shaft.
So...do you guys really think the seal is bad enough that I would cavitate to the point of going only two miles per hour? Or do yall have a suspicion like I do that the bearings are bad in my midshaft? Please help, Thanks, Jacob

 

[MADMAT]

Hell yea its bad! Replace and reinstall with black RTV silicone. That has to be sealed really well.

 

[steve-uk]

that seal looks f'ed!

when you put the pump back together silicone each section together too

the gaps on your impeller to wear ring look good from the photo .. one you have a gap between the impeller and wear ring of more than 1mm you will get cavitation, 0.5mm gap is normal

depending on the mods you have on your ski, looks like a stock prop which is ok with a stock set up, if you have a heavily modded motor, at high rpm the pitch may not be correct which can also cause cavitation

 

[MADMAT]

And add a 13/16-3 prop while your at it. It will put a big smile on your face!

 

[JetManiac]

Replace the pump seal, replace that nasty aluminum stock impeller with a SS one. Stock aluminum impellers are cavitation monsters also.

 

[chriselmore_1]

whos got the best price on pump seals?

 

[Dustin Mustangs]

This has nothing to do with splines. You have air leaking into the pump somewhere. Possible areas for air to sneak in: Pump shoe to hull, pump shoe to pump, wear ring to stator, stator to reduction nozzle, and at the mid-shaft. Make sure all these are sealed up tight as a drum with the proper sealant (if called for in manual). Your impeller is a little beat but not near bad enough to cause what is happening.

 

[steve-uk]

whos got the best price on pump seals?

www.greateryamaha.com

 

[tipafew]

Yes, PLEASE replace that pump seal and that prop. Even if you don't spend the big buck for the "ideal" prop, you can probably find a nice Solas I or something on here for well under $100. It will make a big difference.

 

[oxnard111]

I have a great condition pump seal $14 shipped... PM me.

 

[TexasTexas95]

Sorry, I already ordered the pump seal on Monday. It should be here today. Thanks yall for the input, this is driving me nuts. I am also looking into an impeller which will also go on before i fire this sucker up and try again. I will examine all areas for cracks and leaks too. When I put on the ride plate and intake grate I sealed everything so the bottom of my hull had no where to allow water in except the intake grate.

 

[nightrider05]

I have a 13-18 Pitch Solas Impeller.It started life as a different pitch but has been repitched and its etched inside...blades look great. Would sell it pretty reasonable. PM me if interested.

 

[DK-Freestyle]

I had this same exact problem on my square a couple months ago. The pump seal was bad, and cause an air leak into my pump. I changed out the pump seal and it's running great now.