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  1. #1

    The ongoing 97 SLT780 saga....

    So, I think I may have come up with some of what is going on with my skis, let's see what you guys say.

    To catch everyone back up: bought two '97 SLT780's. Machines looked good and started up, bought them for a decent price.

    Got them onto the water and performance was terrible.

    Went ahead and rebuilt fuel and carbs, seemed slightly better, but still no dice.

    Took the skis to a well respected local PWC mechanic. He went through the engine and found a problem with leaking gaskets arround the reeds and intake manifold.

    He got them back to me earlier today.

    Put them back on the water and while the engines are pretty smooth now, we still seem to have very poor performance.

    Took them out of the water and took the whole jet pump off and go over everything.

    Here is what I have:


    Ski 1:

    4400RPM & 28MPH at WOT

    Revs past 6500 Out of water (very quick test to verify ignition, etc)

    Low Compression (100-95-100) but runs smoothly. Needs a jug kit this fall.

    Stock intake grate, ride plate, etc.

    Non-stock impeller (Polaris 5131092) in decent shape (some small nicks)

    Clearence to wear ring varies between .008 and .024 (not a typo: point zero zero eight to point zero two four)

    Water in nose-cone bearing assembly, but turned smoothly before disassembly. Impeller was loose, allowing play, which is what I believe resulted in uneven wear on the aluminum extension tube.

    Driveshaft in good shape.

    Wear ring is in poor condition.

    Stator seems trashed.


    Ski 2:

    4300RPM & 25MPH at WOT (If you pump the throttle between 1/2 and full throttle it will eventually come alive and give you 35 MPH @ 5100RPM, but it will soon drop back to 4300, particularly if you even slightly turn.)

    Revs past 6500 Out of water (very quick test to verify ignition, etc)

    Passable Compression 130-125-130

    R&D intake grate, stock on the rest (ride plate, etc)

    Stock Impeller (Polaris 5131371) with a variety of nicks and chips, some over 1/8" in depth.

    Clearance to wear ring is a consistent .024 around all points.

    Water in nose cone bearing assembly, seals and bearings appear poor.

    Driveshaft in good shape.

    Wear ring is in very poor condition

    Stator seems trashed.






    So what do you guys think?

    My biggest question is, does the stuff above, that is to say broken stators, poor impeller clearance, nicked/non-original impellers, and water in the bearing assemblies together lead to the abysmal performance I am seeing above?

    If fixing these will most likely get me back to decent performance I will keep putting money and time into it, if my performance/speed numbers don't seem to match up to the issues I have found, I would love any other insight you guys may have.

    What about Ski2 occasionally being coaxed into 5100RPM, but normally only getting 4300? Do I need to look elsewhere for that?

    Thanks for the help guys!

    If someone had a second to pass me some recommendations tonight I would be so greatful..... I may begin looking for parts in the morning if there seems to be some correlation between my damaged parts and my observed performance.....

    Again, thanks so much for helping me!

    Karl P





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  2. #2
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    THe pumps are junk. Send out the 371 impeller to be redone. Try to find another good 371 impeller. Get 2 new stators. A bad pump should make it easier to get full RPM, which should be around 6500 or better. I dont know that the 092 impeller is.

  3. #3
    BlueFishCrisis's Avatar
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    Quote Originally Posted by BryanP View Post
    THe pumps are junk. Send out the 371 impeller to be redone. Try to find another good 371 impeller. Get 2 new stators. A bad pump should make it easier to get full RPM, which should be around 6500 or better. I dont know that the 092 impeller is.
    An old thread identified the 092 as stock off a 96SL900 or a 8/20. This doesn't quite line up with pics I have sean as the manual states the 96 SL900 has a 3 blade, while the 092 is a 4. Definitely get new wear rings and stators. You should check your carb settings and see if you can identify how piston wash looks..... If you can first get your hands on one good wear ring, try that out first. Go one step at a time, although a whole pump setup may be a better deal....

  4. #4
    But the general consensus is that the more damaged the stator/impeller get, the higher your rpm's get, not reverse?

    If so, I am leery of pumping money into fixing the jet pump assemblies just to get them back into the water and find that while they needed to be done, my performance is still in the toilet.

    I did try taking off the MFD's and that didn't help, but what about the limp mode? Any chance it is keeping me around 4300~4400 RPM?

    Any other electronic thing which will limit RPMs?

    Karl P

  5. #5
    BlueFishCrisis's Avatar
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    Quote Originally Posted by iamkarlp View Post
    But the general consensus is that the more damaged the stator/impeller get, the higher your rpm's get, not reverse?

    If so, I am leery of pumping money into fixing the jet pump assemblies just to get them back into the water and find that while they needed to be done, my performance is still in the toilet.

    I did try taking off the MFD's and that didn't help, but what about the limp mode? Any chance it is keeping me around 4300~4400 RPM?

    Any other electronic thing which will limit RPMs?

    Karl P
    Excessive wear ring clearance and bad stator / impeller condition will result in higher RPM, I agree. The fact that the ski will rev past 6500 out of the water indicates that they are NOT on the rev limiter. It would stop at about 4400 in the water or Out. You can pull the grey wire in the ebox if you still think this is the case, but I don't think so. It sounds from your description like a fueling / carb issue on both skis. I can't remember previous threads.....Have you performed carb rebuilds, have you reset your carbs to factory settings, and have you looked at your piston wash??

  6. #6
    johnsonmtz's Avatar
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    The 092 impeller was a special, non-stock impeller from Polaris. It was spec'd for engines making greater than 95HP. Basically, the pitch of that impeller is too tall for your engine that just does make 95HP and it's on a boat bigger than it was intended. All of that combined can lead to an engine that won't reach max RPM.

    Get the right impellers on the skis, fix/replace the pumps, and then see where you are.

  7. #7
    I redid the carbs and fuel systems, including pumps, fuel selectors, etc. I had my mechanic look at the carbs as well and he found them to be in great shape. Piston wash looks ok.

    I'm at a complete loss at the moment. Going to talk to zigler/watcom again here in a moment.

    Karl P

  8. #8
    Just went and did a quick test

    Ski 1 will very briefly go above 4400 RPM out of the water but then it seems to "miss" and come right back down to 4400 RPM, even out of the water.

    Ski 2 will go above 4400RPM, but only sometimes, other times it seems limited. Again out of the water.

    I obviously kept my out-of-water runs to less than 20 seconds, with a cooldown period, etc.

    Thanks,

    Karl P

  9. #9
    BlueFishCrisis's Avatar
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    Quote Originally Posted by iamkarlp View Post
    Just went and did a quick test

    Ski 1 will very briefly go above 4400 RPM out of the water but then it seems to "miss" and come right back down to 4400 RPM, even out of the water.

    Ski 2 will go above 4400RPM, but only sometimes, other times it seems limited. Again out of the water.

    I obviously kept my out-of-water runs to less than 20 seconds, with a cooldown period, etc.

    Thanks,

    Karl P
    Any flashing lights on the MFD? You can try disconnecting the grey wire in the eboxes to see if that corrects the problem. If it does, you potentially have a bad LR module(s)

  10. #10
    No flashing lights, although they do come on briefly when starting the machine. will try the grey wire.

    What is the LR Module(s)? CDI? Something else?

    Karl P

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