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  1. #1

    Kind of low rpms, is it my impeller?

    I just replaced my impeller on my 03 gtx with a 12/20 solas (that is what the shop said to get) and I am running really low rpms. I have read a lot on here that 6800 is the magic number for the 03 gtx when it has a supercharger problem. I am running at 6800 and cannot remember what it was before the impeller (I just bought this pos) so I don't know what is wrong. I also cannot get the speedo to get over 60, it says 55 most of the time but when I run next to the 03 waverunner they are almost running the same speed with his pulling on me and being faster. He said the speedo on his read 74 so I don't know wtf to do now, do you think something is wrong with my sc? I believe that it may be, it just does'nt pull very hard, and if so how much money are we talkin......... Temp was about 90 and water temp 85 or so it said.
    Last edited by super_gtx; 07-06-2008 at 09:42 PM.


  2. #2
    Any ideas? This question I know has been asked a million times, I am just confused because it will almost run with the waverunner.

  3. #3
    King_Of_Fun's Avatar
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    The normal rpm on a stock '03 GTX SC is 7550-7600. At 7600 you should be seeing 59-61 mph. With a few mods, you can get 61-64. If you lost rpms when you changed impellers, it's due to the impeller having too much pitch. I suggest buying or borrowing a GPS to see your actual speed... Ron

  4. #4
    R88ory RXP's Avatar
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    I think that the wave runner maybe reading in kilometers per hour and not mph. if he was running 74 mph he would be well gone. My friend has a yamma and his reads in kmph. mayb thae prop you have is a touch too steep for your ski which will hold your rpm down. My 02 R88

  5. #5
    Banned User
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    Pop off your SC inlet hose and try to spin your SC, if it spins freely your in trouble.

    Alex

  6. #6
    jpeconsult's Avatar
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    Two things...

    1) a slipping SC could/would give you 6800 RPMs and 55 MPH. The ski baicaqlly performs as if it does not have a SC on it. Take the inlet hose off the SC and stick your finger in the SC and try to spin the SC impeller. There is a slight jiggle, that usually will make you wonder if that is slipping, and it is not...You are looking for any rotation of the SC impeller. If you can rotate that impeller at all, you need to replace some parts in the SC if not going ahead and rebuilding the whole thing.

    2) Since we do not know your pre 12/20 RPMs, and now you have low RPMs, we are guessing you did not have the low RPMs to begin with. Give us alittle background/history as to why the shop wanted to replace the impeller.

    I have a moderatly modded GTXSC (185) currently with a 13/20r impeller that is working perfectly.

    Check that SC like Alex said...It will at least narrow the problem down for us.

  7. #7
    Ok just checked the inlet on the supercharger and it does not spin freely but it will spin but you have to almost cut your hand and push hard as hell to make it spin. I changed the impeller out myself and that impeller is what he said I would need. What am I looking at now, damn I wish I could remember the rpms what it was before but I was a newbie before I absorbed all this knowledge.

  8. #8

  9. #9
    R88ory RXP's Avatar
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    Quote Originally Posted by super_gtx View Post
    Ok just checked the inlet on the supercharger and it does not spin freely but it will spin but you have to almost cut your hand and push hard as hell to make it spin. I changed the impeller out myself and that impeller is what he said I would need. What am I looking at now, damn I wish I could remember the rpms what it was before but I was a newbie before I absorbed all this knowledge.
    This is normal that you can turn it aroud about 1 tird of a turn on the sc wheel. This is because you can actualy turn the engine over between valve lifts on the cam. basicaly the movement that you feel is the distance in rotation between valve lifts. the 4 tec engine was designed to stop with all of its valves shut when switched off. You can only turn it becaus the sc gear is so small compared to the flywheel so the gear reduction is very high. R88

  10. #10
    jpeconsult's Avatar
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    I have never been able to rotate my SC impeller. I understand about the wiggle/play in it, but to be able to turn/rotate it???

    I thought that any rotation of the SC was bad. I know this has been discussed before man times, but I thought I understood correctly.

    Super GTX, will it spin more than 1/3 rotation as mentioned by R88ory RXP?

    I did see a member's signature that mentioned he had a 12/20 on his GTXSC, so maybe it is not improssible.

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