Please Help Me try to Diagnose cavitation problem w/ pics

[scoogie_scott]

Hello all,

I have a 98 GTI that is having cavitation problems. When I took it out to the lake the other day, I was only able to get it to plain out once in the 20 mins I was out on the water. I just rebuilt the carbs and replaced the fuel lines so everything is good their. Based on what I've found trying to do a little research, it seems it could be a bad wear ring. However, I'm no expert and wanted to get the opinions of others before I start buying any parts. The edges on the impeller are nicked up, but compared to the only damaged one I've ever seen before this one looks good (that one was actually missing chunks of the blade). Please check out the pictures I have and let me know what you think.

 

[cli55er]

did you measure clearance between impeller and wear ring?

 

[scoogie_scott]

Not yet. Where can I pick up some of those feeler guages? I may try to get some tonight and measure it.

 

[cli55er]

autoparts store.....harber freight tools.....northern tool. maybe a hardware store if they have an auto section. i just used a generic gauge tool of my dads from eons ago. i can tell you now though my blades are much closer to the wear ring than yours is. my impellers just got redone and the pumps just rebuilt too. i have a max of .016 clearance at the biggest gap and much less at the blade tips.

 

[txporkchop]

Clearance looks perfectly fine, but you're missing chunks around where it meets the hull. If that's the case then you're just sucking air. Needs to be replaced(don't forget the neoprene seal) and rtv around the hose connections.

 

[Minnetonka4me]

The 98s dont need a neo ring, nor any RTV...they have the support plate.

On the bigger machines it becomes more and more important to have a tight fitting wear ring so check that. You describe a much wore problem than that though.

Its more than likely the carbone ring or the boot where the driveshaft goes thru the hull. Very less likely...the sealant around the pump shoe is failing. You can just put a coat of sealant along the seams and if it fixes the problem ride it till it gets bad again. then...you might want to pull it all apart and do it right. Its a complete PITA though.

 

[scoogie_scott]

The 98s dont need a neo ring, nor any RTV...they have the support plate.

On the bigger machines it becomes more and more important to have a tight fitting wear ring so check that. You describe a much wore problem than that though.

Its more than likely the carbone ring or the boot where the driveshaft goes thru the hull. Very less likely...the sealant around the pump shoe is failing. You can just put a coat of sealant along the seams and if it fixes the problem ride it till it gets bad again. then...you might want to pull it all apart and do it right. Its a complete PITA though.

Now that you mention that, I noticed that clamp 6 (in picture below) was off so I put it back in place and tightened it up real good before I took it out to the lake; however, once I got back home it had come off again. It's done that to me a couple times just while running them on the trailer. Could there be some reason that I'm not seeing that is causing this clamp to keep coming off? I'm pretty sure I'm putting it on there dang tight because I'm using a socket wrench.

 

[Minnetonka4me]

Just replace it. DId it work better when you did have it tight?

 

[scoogie_scott]

Just replace it. DId it work better when you did have it tight?

I know this a month old but I've been busy here lately and haven't had any time to work on the ski anymore. I plan on working on this problem again now. I know you mentioned the carbon seal and/or boot could possibly be bad. If I pull it all out, what are the signs of them being bad? If one or both of them need to be replaced, what other parts in that diagram should be purchased to replace with them? Thanks for the help.