Super Jet Impeller came unscrewed while riding?

[OCD Solutions]

Has anyone ever heard or experienced an Impeller spinning itself off while riding? It happened to a buddy last weekend and we are still trying to figure it out. We thought he snapped a drive shaft but quickly realized it was simply unthreaded. No damage at all, just thread it back on.

Normal operation should tighten the impeller onto the shaft not loosen it right? I could understand if the motor suffered a sudden seizure too that the impeller could break free as well but that was not the case either. Ski was running strong before and free revving after...

signed..."Stumped"

P.S. It was a Skat C75 13/19 pushed by a SS865 in a Superjet.

 

[restosud]

vibrations coupled with insufficient initial tightening torque could cause this.
has happened before.

 

[Boris]

Rev it out of the water much ?

 

[OCD Solutions]

Rev it out of the water much ?

Other than riding surf not really, just brapping on the trailer to clear the exhaust. The rider was jumping the ski at the time though. It wasn't the owner riding at the time either.

 

[McDog]

Is it possible the motor was running backwards?

 

[OCD Solutions]

Is it possible the motor was running backwards?

Not sure, I wouldn't think so though.

I know the impeller wasn't torqued down to spec but put on hand tight and then snugged up slightly. Proper torque is only something like 17 ft/lbs anyway. we did a bunch of parts swapping earlier and were playing around with different ignitions so maybe it kicked back enough to break it free.

Wouldn't it snug itself back up the first time the engine was revved up? If there were 3-5 threads loose when the ski was revved, the impeller would spin down on the threads and have more than enough to momentum to seat itself with far more torque than 17 ft/lbs.

 

[WFO Speedracer]

Revving the crap out of it with the a$$ end out of the water and then dropping the ski back in the water would screw it back on, but there is a risk of damaging the flywheel key in the process.

 

[OCD Solutions]

I just don't see how a impeller that has been run for 6 months plus behind a SS865, suddenly comes loose in the first place. There are tons of threads on here of it taking days to break loose a stubborn impeller with many eventually being cut off the shaft even.

 

[orangefinger]

Is it possible the motor was running backwards?

I second this, running backwards...

 

[227]

I second this, running backwards...

If the motor was running backwards then the prop also would have been turning backwards and the thrust (If there was any) would be in reverse? Since he was riding right before it happened then This doesn't seem like the case.

 

[Crab]

Always torque them on properly.

 

[oxnard111]

A B1 I parted out had an impeller that was completely loose when I pulled the pump. The impeller was just floating on the shaft.

 

[OCD Solutions]

If the motor was running backwards then the prop also would have been turning backwards and the thrust (If there was any) would be in reverse? Since he was riding right before it happened then This doesn't seem like the case.

That was the same logic I was using...

One of the reasons we were swapping components that day was to find a fix for an intermittent starting issue we suspected was part of an Ignition issue. It is completely possible that the problem was actually a loose impeller that was or wasn't binding the wear ring at different times adding drag depending on where it was sitting at the time. wouldn't that be a kick in the junk...:nutkick:

 

[Midlake Crisis]

My theory / guess / idea: maybe he jumped straight up and landed on the tail, and the force of the water entering the nozzle from the opposite direction busted it loose.

 

[speedysprocket]

When I took the pump off my Octane after I bought it, the impeller was only on the impeller shaft a few turns. That's a little different setup than the yamaha though, and all the bearings inside had fallen apart too...

 

[OCD Solutions]

My theory / guess / idea: maybe he jumped straight up and landed on the tail, and the force of the water entering the nozzle from the opposite direction busted it loose.

I could get on board with that. He was riding like that at the time but this was a surf ski and has done that plenty of times from much higher up.

 

[Idok]

B..whose boat???

common on kawis but thats a little strange.....


the impeller MUST have been seated initially or else the pump wont fit in properly...Im with you on the torque, I just tighten them down but dont torque...never had a problem though

strange!

 

[OCD Solutions]

It was Scott's red ski. Andy was taking a quick burn on the channel at Tybee when it happened.

 

[Idok]

It was Scott's red ski. Andy was taking a quick burn on the channel at Tybee when it happened.

scott if youre reading theis maybe you need to lean our your carbs a little

 

[OCD Solutions]

scott if youre reading this maybe you need to lean our your carbs a little

:haha: BWAAAAHAAAAAAA!!!