Super Jet Cavitation problem?

FlightPlanDan

FlightPlanDan

Don'tTrustAfartAfter50
Location
Crescent Beach, FL
O2VW1.8T said:
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
Click to expand...

I'm a round nose guy, but that prop sounds fine to me.
I run almost the same set-up (62t) with a skat swirl 12/17. (6mm cutback from skat...lol. They're not that precise)
13/17 is stock pitch for my rn.

Maybe we have the same problem!
 
O2VW1.8T

O2VW1.8T

Location
NC
ok i think i might have found my problem, i pulled my carb apart and found the filter inside was clogged about a 1/4 of the way. So i clean it out, adjusted my high and low setting and now it starts and runs before it would die. Also now when i do a WOT hit its nice and crisp, cant wait to ride it now...
 
Dorny119

Dorny119

Location
Connecticut
I would like to revive this post. I think I may be having the same issue. I did a compression test and found 165/165 in both cylinders. Stock 701 with a B pipe, a 9/15 hooker and worx scoop grate. It seems to be well tuned for throttle response. I get zero hesitations and it does not seem to be loading up. If I do a launch from a stand still, it just does't pop like everyone claims it should. I have ridden other skis and felt more pop. The hooker 9/15 should have excellent hook up. Also, If I do a nose high jump and pin it when I land, my ski doesn't immediately pop back out of the water. It just sits there and screams for a second. I checked the clearance between the ring and impeller, and found less than 0.010" clearance which is good I think.

On another note, while I idle through no wake zones, if I hit the throttle ever so slightly and bring the rpm's up a tiny bit, the ski vibrates like CRAZY! But my motor is well aligned using the Wammer's method with a straight edge. Maybe this vibration is in correlation with my pump hook up issue? Thanks!
 
Dorny119

Dorny119

Location
Connecticut
Ok, I did some more reading and found that I have an issue that I did not know was an issue. The engine coupler and the midshaft coupler have a large gap between them. My engine is moved back as far as it can go. I'd say the gap is a full 1/2 inch.

So my question is, how do I slide my midshaft back into place? Thanks!
 
Harbor

Harbor

Location
Stockton
Dorny119 said:
Ok, I did some more reading and found that I have an issue that I did not know was an issue. The engine coupler and the midshaft coupler have a large gap between them. My engine is moved back as far as it can go. I'd say the gap is a full 1/2 inch.

So my question is, how do I slide my midshaft back into place? Thanks!
Click to expand...

Remove what's necessary to allow engine to slide forward, then
Unbolt and slide your engine forward enough to get your midshaft out, use a press to push the midshaft out some, should hang out the back about 19.5mm

Might check your engine mounts before you unbolt the engine, try to pry under the bed plate at each mount and check for tearing in the rubber. Or try to lift or tilt the engine sideways by hand.

Shims between bedplate and mounts so be careful to keep seperated and put back same location.. you may already know all this though
 
Dorny119

Dorny119

Location
Connecticut
ok thank you! I wonder if this may also be contributing to my cavitation issue. Perhaps the seal around the housing is bad. I'm excited to see if this does the trick along with a new pump seal. Should be testing it out end of next week.
 
Dorny119

Dorny119

Location
Connecticut
Well, I took the pump apart and the pump seal looks good. I put a bead of silicone all the way around and assembled the pump. I took the ski out on the water to find the same issue. It still has a lack of pop from low speeds. I am ruling out carb tuning for now because I can hear an immediate increase in RPM when I pin it hard (I can try to post a video tonight of me pinning it at low speeds, and you can listen for yourself). I am starting to think that my impeller is not what I think it is, and I will send it out to impros to be checked out. I'm also going to try rebuilding my mid-shaft assembly. Is there a possibility I am sucking air through the seals if they are bad? Thanks!
 
Dorny119

Dorny119

Location
Connecticut
Hi all! Now comes the time of year that I don't ride so all I can do is think about riding, and talk about riding. Well, I am fairly confident it was never a cavitation or "slipping" issue. Here is how I know. I was able to get a significant amount of low end pull by improving my motor's low end power. Yes I know, that's how it works! But if it was a problem with the pump pulling air, or cavitating, I think that an increase in engine power would not translate to better pop out of the water; it would just create more air bubbles.

The interesting thing is HOW I was able to get more bottom end. I was out on the river one day and noticed that I had some crazy low end pull that I had never felt from my ski before. This ofcourse made for a fun day of beginner flat water! Sometime later in the day I noticed that there was only a tiny stream coming from my bypass. I stopped and looked at the orifice, and noticed a little vegetation blocking the exit. So, I pulled that out and sure enough there was a nice normal stream.... But wait, WHERE DID MY POWER GO!? Was it resulting from my blocked bypass!? So the next day I made a restrictor at work (I think the hole was somewhere around 80 thou). When I tried it in my ski, yup there was my bottom end pull again!

So, does this mean that more water to my water box results in better low end power? It sort of makes sense. More back pressure. But I have a Factory B Pipe with the top screw opened up. I thought that was supposed to maximize water flow for low end? Any thoughts?
 
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