Cavitation problem

[Whister]

I just got a 96 Speedster with twin 720s, and it is a slob out of the hole. Once it gets going it goes allright.. it's lots of fun and turns on a dime, but the boat takes about 15-20 seconds to get up on a plane before you can give it more than 1/3 throttle.

The wear rings are good to the best of my ability to inspect them, and the boat leaks no water into the hull when anchored for an hour or so. Can it still be sucking air in through the accordion boot seat and not leak when sitting?

Also, on one engine the prop must have chewed something up and damaged the channel after the grate. Here's a few close ups. I probbaly need to to get in there with some epoxy and smooth out the damage in there. The impellers don't look too bad but I've heard that the Skat Trak 14.5/22.5 is a nice improvement, so I plan on ordering those tomorrow.

Here's the right side impeller and channel

The left isn't as bad

 

[kustomkarl]

I looks like it could use a little smoothing in that jet pump. Here are the specs for the jet pump wear ring. Wear Ring clearance for your seadoo 1.0 mm or (.040in) Measure the clearance at the center of the impeller blades, with a 12” long gauge. Measure the clearance from the venturi side of the jet pump.

I hope this helps you out. Let me know how if you need any more help.

Karl

 

[Whister]

Thanks! I'll have to get some longer gauges.. mine are a little mechanic's set.

 

[kustomkarl]

You should be able to buy one at like Auto Zone, Napa or Sears if one is close.

Karl

 

[robin savell lloyd]

I am not sure on this one. The wear rings look like they may be brand new. The impellers look original but if they do not apair to look damaged the boat should still have a good hole shot. If rpms come up very good on both engines on hole shot and you are haveing cavitation I would look into pump seals and threw hole seals but I am not expecting it to be threw hull seals but I can sure be wrong. It allso looks like pumps may have new sealent on them from when they replaced wear rings. the damage needs to be looked at very well for cracks and so forth and need to be repaired. A good product I like is called marine-tex. It is very strong and comes in white. Read up on it before you use it because there are tricks that you can do to save time and make it look like a profesional did it. If damage was there when new wear rings wear installed I would wonder why they did not fix it. :cheers:

 

[Whister]

The RPMs come up great on both engines. It's like driving an old pickup truck in the snow trying to get it to accelerate though. Can the pump seals and threw hole seals be bad and still be dry in the hull? I thought if the jets were sucking air from somewher ein the hull that water would leak in there when the engines are off... which it does not.

 

[robin savell lloyd]

I see the threw hull seals as you do but I can be wrong If they do not leak in the boat than I would not think they could suck air. Now if the pumps do not have a good seal they will not leak in the boat but will have bad cavitation. You have 2 engines you should have a lot less cavitation than I do but yours seems very bad for some reason. I would repair the damage and reseal the pumps and see what that does.

 

[Whister]

Where are the pump seals?

 

[robin savell lloyd]

when I looked up your model I did not see a part number for a seal or sealent used on pump but there has to one or the other or both some times. You need to find out what is required to seal pump and I will look some more allso. :cheers:

 

[Whister]

I've got Skat Trak 14.5/22.5s, new pump seals on the way, plus I am going to repair the damage in the jet pump chjannel while the props are off. I'll take it out this weekend and report back how it goes!