Super Jet Cavitation problem?

O2VW1.8T

O2VW1.8T

Location
NC
So im having a issue with my ski, it just doesn't hook up right at bottom end punch, at mid to top end it hooks very good. I have a RN whole pump assembly, with WSM wear ring(thought it was bad so i replaced it with a new one) freestyle cone, nozzle not bored, protec intake grate, skat trak 13/17 swirl cutback 3mm.

Today i installed the new wear ring, put some sealer on the seal to the hull, all looks good but it just doesn't hook up. Is it my prop if so what should i try, i had a 10/18 it did the same thing... I ride my friends ski's and all of theres hook like crazy compared to mine.

The ski is a 95 SN, 61x 701, protec head, b-pipe, water box, stock carb
 
munki63

munki63

Epoxy is my duct tape
Location
Canada
You should do a compression test, In the past I had a set-up that took a bit to get going but when it did she ripped! Turned out I was 20psi low on one cylinder
 
kevbo

kevbo

Location
dfw
Is the problem lack of power or lack of hookup? Cavitation will be felt as excessive vibration at low speeds with normal or high rpm. If the pump is smooth then look at the engine.
 
O2VW1.8T

O2VW1.8T

Location
NC
I dont think its lack of power it feels strong once it hooks up. It just doesn't hook up like my friends ski's, like its spinning the tires in the car and then its good.
 
O2VW1.8T

O2VW1.8T

Location
NC
tor*p*do said:
is the pump seal OK? if it is leaking, the ski will do this
Click to expand...
the seal that goes to the pump shoe? If not how can i tell ...


I checked my compression with a bad gauge had a leaky o-ring, will check it tomorrow with a better gauge but it was 150 in one and 145 in the other.
 
tor*p*do

tor*p*do

Squarenose FTW
Site Supporter
Location
NW NC
O2VW1.8T said:
the seal that goes to the pump shoe? If not how can i tell ... Yes, you should have checked it while the pump was out. If it is not soft and intact, it needs to be replaced or it will allow the pump to cavitate.


I checked my compression with a bad gauge had a leaky o-ring, will check it tomorrow with a better gauge but it was 150 in one and 145 in the other.
Click to expand...

compression sounds good, check the seal
 
O2VW1.8T

O2VW1.8T

Location
NC
tor*p*do said:
compression sounds good, check the seal
Click to expand...
Thing is i even put sealer on it, it still felt soft. Im just going to order a new one and if it doesn't fix it i might order a new prop hooker 9/15

Should i pull the pump again and installed it without the seal to check the gap
 
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FlightPlanDan

FlightPlanDan

Don'tTrustAfartAfter50
Location
Crescent Beach, FL
possible that air is being sucked from the engine compartment through a bad mid shaft seal. I've been having similar issues. Replaced everything but the mid shaft after a severe lawn dart. I'm not sure yet. Gonna enjoy riding for now. but I've been told this can happen.
 
D-Roc

D-Roc

I forgot!
Location
Dirty River Rider
yes that old midshaft seal could be showing its age. if the pump gets air from the midshaft or the pump area thru the pump seal it will cavitate. you can shut the ski off and sink the back of the ski and fill the pump area with water. start the ski and do a race holeshot start and see if it hooked up. if it did then do a nose high jump and land and see if trapping air in the pump area will cause it to cavitate. if it does its the seal. if none of this made any difference at all i would be checking the midshaft before buying a prop. now if the pump seal is really bad it may not let you holeshot at all because it doesn't take long to drain the pump area when moving forward. if you get speed and on plane and have a good scoop grate it will feed the pump well enough to not be so noticable. hope this helps. it is not scientific but if how i test for a pump seal leak.
 
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O2VW1.8T

O2VW1.8T

Location
NC
yeah i heard that can cause it also. But i filled the engine compartment with water and didn't see any leaks. I will try it again with the pump out
 
FlightPlanDan

FlightPlanDan

Don'tTrustAfartAfter50
Location
Crescent Beach, FL
Mine won't leak by filling it with water. But I believe it's happening while riding. The force of the pump pulls the air thru. My mid and high rpm ranges are great. It is just slow to hook up at the bottom. Just like yours.
I don't plan on ripping it apart for a while though. It's running well enough to have fun.
 
O2VW1.8T

O2VW1.8T

Location
NC
Yeah thats my problem mid and top are great, its just when i ride my friends skis and see how it should hook its night and day almost. I will try resealing the pump area and if i have time i will reseal the midshaft again..

I mean i still have lots of fun, but it would be more fun with some bottom end hit
 
O2VW1.8T

O2VW1.8T

Location
NC
bought a new gauge and the front reads 163 and rear 160 cold engine. So its not the engine, resealed the packing seal again, put some sealer around the midshaft. Will take it back out and see what happens. Do you think its my prop the 13/17 swirl cutback 3mm
 
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