1999 GTX Limited - Half Speed
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  1. #1
    PWCToday Newbie
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    1999 GTX Limited - Half Speed

    Was on water with subject ski which was running fine. Then it seemed to go to half speed (topped out at 30mph) full throttle and won't go any faster. Looking for ideas to troubleshoot what might be causing this.

    Has all new fuel lines and has been running just fine. Starts up just fine as well.

    Any help greatly appreciated.

  2. #2
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    Re: 1999 GTX Limited - Half Speed

    It maybe running on 1 cyl. change plugs and ensure both are firing. check compression on each cyl.

  3. #3
    Resident Guru SpitAndDirt's Avatar
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    Re: 1999 GTX Limited - Half Speed

    What is the history on the carbs? Ever been removed and cleaned? Absolutely need to verify that the tiny internal carb filters are clean.

    How many hours on the ski? 150 seems to be the magic number for rebuilding.

    Definitely perform a compression check.



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  4. #4
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    Re: 1999 GTX Limited - Half Speed

    You have described how a ski runs with only one plug firing.

    Or could just be a piece of debris is sucked up in the grate.

    Also when oem style wear ring has delaminated.

    A quick way to confirm if plugs are good while out riding is just grab each one after engine has been running. If a plug is not firing, it will be a lot cooler to the touch than the other one.

    Usually changing the plug fixes problem. If not, check to confirm new plug has spark. If weak or no spark, remove boot and cut wire back 1/4". If still no spark, check coil.

    Without more detail this spark plug is what I would suggest first. Then check to make sure nothing has been sucked up in the grate or pump.

    The next thing is to check the wear ring. You didnt state if the motor was reving very high or sound any different than before. You can shred the wear ring and also run like at half speed.

    Sometimes the ski can seem fine even with wear ring destroyed. If motor is reving up a lot but ski is going slow, this is the next thing to confirm. Skis dont always cavitate when wear ring has delaminated or disintegrated.
    Last edited by Seadoo timebomb; 07-15-2020 at 04:27 PM.

  5. #5
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    Re: 1999 GTX Limited - Half Speed

    is it possible one carb working and one not? They were rebuilt last summer and maybe have 20 hours on them? I'm going to be able to check / test them this weekend finally>.

  6. #6
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    Re: 1999 GTX Limited - Half Speed

    Engine wasn't revv'ing any higher than normal at all.... I can't remember if I replaced the plugs or not last summer. Could something be causing a plug t go bad?

  7. #7
    Resident Guru SpitAndDirt's Avatar
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    Re: 1999 GTX Limited - Half Speed

    Replace plugs every season. They're cheap. Also, inquire with Chris at Watercraft Magic for their jet kit and Prox filter setup for the 951. The stock airbox lends itself to ingesting water on some skis.

    Sent from my SM-N975U using Tapatalk
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    Rides: 2 x 96XP // 99XPL // 02RX Currently rebuilding
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  8. #8
    Resident Guru SpitAndDirt's Avatar
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    Re: 1999 GTX Limited - Half Speed

    Something else I forgot about. There should be a rubber boot that fits completely around the exhaust manifold to expansion pipe connection. The gasket there was a possible weak point in that water could spray from the gasket directly down the intake while underway.

    It would have to be pretty bad, but enough water spray would either cause a hydro-locked motor or it could just dilute the fuel/air mixture and the engine might bog down.
    Last edited by SpitAndDirt; 09-11-2020 at 06:07 PM.
    "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed."

    -Robert M. Pirsig, Zen and the Art of Motorcycle Maintenance

    Rides: 2 x 96XP // 99XPL // 02RX Currently rebuilding
    I love my CanDooPro! Take that stealerships!! www.candoopro.com

  9. #9
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    Re: 1999 GTX Limited - Half Speed

    Was able to test this weekend a bit. Compression was good at 150. Tested spark and looked like one was bad. Replaced and then took on water and seemed to have taken care of the problem.

    Thanks for all th assistance.

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