Super Jet Does a bone stock SN Porpoise if its foam is water logged?

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#1
Hi guys, we have a 95 SN in our riding group. Mint, purchased new by the previous owner in 1999. We have had it for a few years and looked after it carefully. Only mod we have done is add a 2008+ stainless impeller. It has always porpoised. A few years ago my brother weighed the ski and it was at 398 lbs with 3/4 of a tank of gas. Scale was calibrated against known weights within a couple pounds.

At even moderate speeds this ski porpoises. It's not particularly violent, but it is a very significant bucking at anything more than a slow speed. It can be unnerving for beginners. From other SNs and pre 08 RNs I remember riding, this one seems particularly bad. I actually don't remember others porpoising at all, they usually are pretty smooth. This is particularly an issue when you try and hustle it around a buoy course and trying to keep the ski in a spot you want it. It bucks and moves around so much there's no improvement you can make to the ski with changing riding position.

When the foam is water logged in a SN, does the added weight at the rear make the ski porpoise more? We know this ski is unusually heavy, and we have seen a slow drip from the bond line after the ski is out of the water. Seems to me if the ski has 30-40 lbs more weight in it, that could impact the ski's balance. But then if that's the case, the SNs would porpoise in a similar manner with someone about 200 lbs or greater on one, 40 lbs more than me.

I know with mods like a intake grate, ride plate ect.. you can help improve things. I'm curious about a stock ski. We've had riders with up to 30+ years of riding experience on it, and all say the same thing. This is rider / body english independent.
 
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OCD Solutions

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#3
Sounds waterlogged to me.

Rider weight would have an impact for sure, especially if they never moved. However, a heavy rider can lean forward and transfer even more weight which would end up being an advantage.

Does it improve at all if you keep the tank topped off? Have you tried adding weight up front, even just as a test? Race Weights were sold in 2lb increments IIRC so I don't think it would take much.

Mine was marginally better after replacing the foam. An extended rideplate helped as well but ultimately shimming the ride plate down in the rear got the best results.
 
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#4
You deffinetly have a water legged, my 98 rn I got from my uncle sat behind a pole barn for years and water logged the ski, both my dad who's around 270lbs and me who's 135 have ridden it and it never seemed to porpoise when riding it, it was like that for a season then we cut her open during the winter and resealed everything.

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#5
Really good info here. I've been reading through old threads and it's hard to get a consensus, info seems all over the place. It does seem that water logged foam can make it worse.

Mdavies thanks for that weight. One other thing we discussed, does the dry weight include the battery. That would be an additional 10-15 lbs if not.

OCD I must admit I haven't ridden the ski back to back full vs empty tank in some time. I don't recall there being much difference.

Jon are you saying your ski got water logged from sitting outside? Rain ect can work its way in? If so, this is good to know. This ski doesn't have many hours, but the lady who owned it kept it on a lift each summer. Periods of time without a cover.

I'm working out a deal to get this ski. It's such a nice mint, unmolested 95. My wife loves it and it's a perfect learning stand up. Once I get it, I'm going to look into the foam for sure. Check for leaks, seal it up. Even now I like the ski for its wonky handling. Makes a nice comparison to my stock 09 SJ.
 
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#6
My ski was originally my uncles and just sat behind a pole barn for 6+ years and it filled up with water and actually froze during winter, it ended up cracking the flywheel cover but amazingly nothing else, I'm assuming it came through the factory fill holes for the foam which were just covered by stickers which were non existent.... after re foaming the tray I ended up glassing over those holes so no more water can get in.....still cant belive that the ice didnt do more damage but it's not taking in anymore water

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#8
Ahhh yes ok that makes sense. I know those stickers. Pretty crazy to have that much water in the hull and have it freeze, I would think much more would happen other than just the flywheel cover getting cracked.

I didn't think there would be a way for the water to get in. There would have to be an obvious crack or issue with the hull/ tray.
 
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#13
I had a similar issue albeit with a lot less water in the tray last year. I weighed about 350 on mine and it did porpoise quite a bit. I put a riva groovy extended plate on it and a single shim and it helped dramatically.
 
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#15
Not for sure if this would help. Mainly just a thought adding a shim to the back of the pump so the nozzle is exiting a fraction down may help, not for sure if all pumps are shimed but i know mine came shimied

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This would probably help but by shimming the rear of the pump you're going to need to re-align your driveline or you'll suffer from poor spline wear. Shim the rideplate and report back.
 
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#17
I agree about the pump wedge, that works for the Kawi sxi pro and xir because the nozzle is independent of the pump feet.

Once I own this ski I'll try shimming the ride plate and perhaps putting an intake on it. Start monitoring how it feels with fuel tank level too. Then start developing a plan for foam/ water removal. I have tried shimming ride plates before on other skis and it's a very incremental improvement. Sometimes its hard to tell a change was made. If normal SNs ride straight and smooth then this is a massive issue. It will be interesting to see if the foam can really hold 60+ lbs of water.
 
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SXIPro

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#18
My SN porpoises like a b1tch as well. I swear it weighs 100 lbs more than my RN. Bounce, bounce, bounce , waah-waah-waah....like the Chinese water torture. I'll be defoaming that pig in the winter and installing pink foam from HD and a couple drains in the back.
 
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#19
There have been a lot of threads about superjet porposing the past few years and it seems no matter how many times you say to ride it harder and learn the OP wants to gut the tray and make the foam pink. Well if you want to piddle f*** around to save 20 to 30 pounds tops on your 30 year old sn go a head.

My 400lbs 91 sn does just fine. A superjet is not an sxr. Remember people got tired of going fast in a strait line around 08 when the real sxr died.

The entire freestyle aftermarket is based around the fact that the superjet in all years is sensitive as sh** to the rider and his input.

It's a 7 foot 2 x 4. The water it's in will put it where it wants if you dont learn how to dammit!

Ok sorry for ranting.
 
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#20
There have been a lot of threads about superjet porposing the past few years and it seems no matter how many times you say to ride it harder and learn the OP wants to gut the tray and make the foam pink. Well if you want to piddle f*** around to save 20 to 30 pounds tops on your 30 year old sn go a head.

My 400lbs 91 sn does just fine. A superjet is not an sxr. Remember people got tired of going fast in a strait line around 08 when the real sxr died.

The entire freestyle aftermarket is based around the fact that the superjet in all years is sensitive as sh** to the rider and his input.

It's a 7 foot 2 x 4. The water it's in will put it where it wants if you dont learn how to dammit!

Ok sorry for ranting.
No doubt does rinder experience make a difference but when a sn is bunny hoping out of the water without you try to or while resisting there is a problem, I'm not for sure if its that bad for him but I have seen it like that, also just got my 9/15 hooker in today cant wait to ride it

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