New/Rebuilt SC question for someone that's done a few

[Greg Moore]

06 RXP, SC fried a few hours after a dealer did 100hr washers. Impeller bearing went, prob not dealers fault since they only did washers and turns out (through engine tear down) this girl had failed ceramics in past.. I bought it dead so works for me..

Question is about bearings. I picked up a supposedly 200hr rebuilt but unused since rebuild SC.. It's a newer version but same size (has different back case number and an oil hole between the o-rings the 06 doesn't have) It certainly looks unused since rebuild, it's spotless all round with no polishing on gear teeth yet and a spotless shiny intake area..

Spinning this by hand to me feels tight. It's dead smooth, zero play in any direction and a slight bearing race sound. It feels like there is preload on the bearings. Have never done one of these SC's but have played with a turbo a few years back. If you spun the turbo by hand it would take several seconds to spool down. This takes just a couple to come to a stop.

Do the bearings in these things have a slight preload on them? If so I'll trust this was built right. Or does a fresh rebuild spin for ages when flipped by hand before it stops turning? I'd hate to tear down a pro rebuild for no reason but would also hate to fix all the motor bits and throw on an SC that will also dump a bearing a few hours after use.

Thanks in advance!

 

[Greg Moore]

No body has rebuilt an S/C a couple of times?

 

[garbonz]

If you read a bit on the site on SC it appears that the SC should be a little bit tight, since is gear driven and not exhaust driven like a turbo. Completely different animal. This is not expert information, but just what I have read. May you can contact SBT or whatever, who rebuild them and ask if you don't get a definitive answer here.

 

[greenhornet2]

my superchargers on my cars spin over smoothly but do have some resistance, they wouldn't spin over for more than a couple seconds before stopping.

 

[Coastiejoe]

MANY of us have had them rebuilt, but not done them ourselves. So most can not answer the question. [MENTION=2]hfgreg[/MENTION] can help with the answer...

 

[68ragtop]

There is a seal behind the impeller that puts resistance on the shaft. So they should't spin free. But there should be zero preload on the bearings & they should be very smooth. It's also very important that the bearings are installed correctly by insuring no force is transferred through the balls & dimpling the races. that will make for a short life on a bearing spinning over 40K RPM's.

As far as I know seadoo is still using FAG bearings, part number 6200 C3 So aside from the washer improvements I don't believe the bearings have been improved or changed at all. I have some from an original 2003 SC & its the same bearing thats in todays rebuild kit. I have one of these kits on order right now, so I can confirm this when it comes in

The hole you are talking about is a later design that I beleive aids in keeping a more adequate oil level in the housing to help with bearing life. But that hole is outside the o-rings, not between them. when installed its positioned horizontally in the engine & is just below the oil spray nozzle in the PTO cover. I have a junk SC in my shop with 40 hours on it, it has the oiling hole & suffered a failed bearing. So if it helped at all, I am not sure? I will say that a failed bearing pretty much destroys the SC. either the impeller thrashes into the housing or the outer bearing race spins & chews up the housing. the whole thing becomes junk & un-rebuildible over two $30 bearings And thats assuming none of the balls make it into the engine & do even more damage.

I love the superchargers, but they sure are delicate buggers.....

 

[Greg Moore]

That's what makes me unsure Got this machine cheap because bearings blew out and owner was quoted a fortune (shop wouldn't touch it unless they did motor too).. This 'rebuilt' has certainly been done, I have no question on that, just don't know if done right. It is dead smooth and yes, pulled the dead SC apart and see the seal is against a large bushing so for sure decent drag there. I also learned the C3 class bearing is loose at room temp, done that way so they can tighten up when hot.

I did put a dial indicator on it and there is about .002" longitudinal play so the bearings aren't under preload, just very close fit. Just not sure if I should hear race noise when spinning it. You'd call it silent in a room with a radio on but it isn't "truely" silent.. Think I will run it up 3-4hrs then pull it again, easy enough to do.

 

[68ragtop]

Yes, I agree the C3 rating is a little loose. I usually clean the bearings even if they are brand new & blow them out. When they are dry, they are noisy. Once they get some oil in the race they are quiet.

So what happened to the original SC, do you have it? if it spit a bearing, especially if its on the gear side then the polymer spacer was no doubt chewed up. Did you find all 7 balls in the SC housing?

I would pull the scavenging (oil separator) pump if you didn't already & take a look inside the pump housing & see if there is debris in the screen & inspect the pump rotor & shaft. If your missing bearing parts they are more than likely going to be in there, or whats left of them. Super easy to do on a 2006 & no new gaskets needed if all is good.

 

[Greg Moore]

Original blew a front bearing so shaft, front and back housings and impeller toast. When I found out the unit already had steels I suspected correctly it had dumped ceramics at one point so pulled motor down. It's going to be getting both pumps, rod and main bearings/bolts and has been totally flushed out. Pulled out enough ceramic chunks to make 1 washer.

I'm not too worried about getting through that end of the motor, just haven't done an SC before and don't know what to expect for noise etc from one. Like I said though, failing someone that's done a few and can describe it accurately I'll just button this motor up and put a couple hours on it and pull the SC and check it again.

 

[68ragtop]

I am rebuilding a 4tec right now had ceramic SC washer failure. This one was abviously driven for quite a while with no supercharger. Maybe it was to get it back to the dock, or maybe from shear ignorance I really have no idea. But only 86 hours on it & the engine was completely ruined. Even the cylinder walls had scoring & excessive wear that would require an overbore to be reused. IMO the the screens before the pumps only prevent large pieces from going into the pump & destroying it instantly, but these washers get so ground up into a fine abrasive pulp that it passes through the screens wrecking everything. Might as well dump a few tablespoons of fine sand basting media into the crankcase.

Sounds like maybe yours wasn't run long after failure, but I have a new respect for how much damage these washers can do to these engines if not shut down asap.

Whats seems ignorant to me is in 2003 the first SC's had .015" thick ceramic washers & those where no doubt failing & the fix was going to a thinner shouldered shaft & .020" ceramic washers. Really? This problem would appear to be known very early on & to allow those washers to stay in there thinking .005 thicker would be the fix is kind of crazy. Maybe there was a different reason for the change of washer thickness early on but the whole thing in hindsight seems nuts that these were ever allowed to stay inside the engines, especially with the SC positioned in a part of the engines that is essentially a meat grinder. the odds of broken washer parts making it tho the bottom area of the PTO case is pretty slim.

They should have gone to the metal washer R&D a few years earlier than they did. Just my opinion of coarse.

 

[Greg Moore]

I think a lot comes down to shit luck when they blow. Depending on luck, the machines angle at the time etc, the broken chunks can drop clear to the bottom or get caught up in the cam chain. The latter would be worst case as not only is the cam gears and chain now toast too, the pieces are reduced to very small fragments. From the scaring on the front pump, chunks bigger than the screens openings can weasle their way through. This motor had clear damage to #1 main bearing. A slight score on the journal from the oil hole and around about 1/2" from it, but the bearing showing copper.

Good luck for me in that I feel this motor will be restored with about $400 in parts and several hours (aside from a destroyed SC) but I can literally make a complete washer from the chunks I pulled from the bottom. There was all this plus 2 more chunks not in the picture. These probably could have lived forever in the bottom of the motor but still, poor design all round. An external Roots style supercharger would be way better.