Cavitation

[Lil Dick]

My ski Cavitates pretty bad and can't figure out why I run a 62t with nynja piped and dual 44s with a mag pump and 9/15 hooker the pump seal. Seals tight against the pump shoe do the light test around the seal and shoes no light everything is brand new and shimmed right just cavitates bad still can anyone tell me what to do now


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[bobob729]

Wear ring possibly?

 

[Lil Dick]

Wear ring is a brand new stainless wear ring whole pump drive shaft prop and wear ring were bought new


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[bobob729]

What about the pump shoe is there in lines where it bonds to hull?

 

[Lil Dick]

Yea the pump shoe is sealed nicely to the hull everything seems nice and straight the pump seal has a nice seal against the pump shoe. Someone told me I should still put silicone in that void where the seal and pump shoe meet I'm going to try that and hope that's it


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[bobob729]

Ive seen that cause cavitation and I always seal my pump seal also just to be safe

 

[Lil Dick]

Yea I'm going to do that and hope that's the issue


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[Dartman]

always check your midshaft housing also...could be cracked and sucking air through through the shaft tube

 

[JetManiac]

Ive seen that cause cavitation and I always seal my pump seal also just to be safe

I always use silicone between shoe and seal as well.

always check your midshaft housing also...could be cracked and sucking air through through the shaft tube

Yes, a separated housing can cause this as well. We always silicone housing to bulkhead as well.

The spinning impeller creates a low pressure, and it is easier to suck air than water so any place to suck air it will.

 

[kevbo]

Make sure the grate bolts have not popped through the pump shoe.

 

[Philip Clemmons]

Is this in a SJ? On A/M hulls you really have to press the pump forward as you tighten the pump bolts. Agree with sealing the pump seal.

 

[Lil Dick]

It's in a aquabot


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[Philip Clemmons]

You need to be sure you are pushing the pump forward. Sometimes you need to enlarge the pump bolt holes to allow movement. I put my ski against the wall, push on the nozzle with all my strength and weight, while my wife tightens the bolts. This is normal for A/M hulls. My KDX would cavitate if I did it any other way. If your bolts are touching the rear of the holes in the pump, the hole size is limiting your ability to push it forward and compress the gasket.

 

[Lil Dick]

Yea all the holes have been enlarged the seal seems to be tight I'm going to try the silicone on the gasket first and if that doesn't fix it I'll try and push the pump in more


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[Philip Clemmons]

You have to push it in hard every time. If you are taking it apart to silicone the gasket, be sure and have someone help you tighten the bolts while you force it forward as hard as you can. I use a towel because I push so hard it hurts, but it works!

 

[shadowrider]

Yea all the holes have been enlarged the seal seems to be tight I'm going to try the silicone on the gasket first and if that doesn't fix it I'll try and push the pump in more


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Are you sure it's cavitation? My ski, I swore was cavitation, but it was a poor running engine and made it feel like it was cavitating. It would only "cavitate" when I would start out or tail stand it. I got the motor running good and it does not cavitate now.

 

[Lil Dick]

I'm pretty sure it's cavitation but then again it only does it when u start off or give it a quick throttle response and carve


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