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  1. #1

    Exclamation 1999 Gp1200R water temp problems....please help

    Hi guys, quite new to the whole jet ski thing but mechanical minded so understand the basics.

    Have taken my 1999 GP1200R out twice now and both times the warning light comes on and said 'water temp' this happens quite quickly, usually after 20 minutes of trundling around at 5000RPM (not going crazy)

    I can touch the exhaust and engine without getting burnt so its not over heating, and its pumping water out of the side of the hull, so its pumping ok.

    I have heard it could be the cat converter, but i don't think mine has one as she's an old girl.

    I took the sensor out of the side of the exhaust pice that has 'YAMAHA' stamped into it and it looked in good nic.

    Any help would be much appreciated. thanks a bunch guys

  2. #2
    OzarkYamMonster's Avatar
    Join Date
    Oct 2012
    Lake Of The Ozarks
    Hello & welcome to the Hulk. The GP1200 is a solid performer & normally easy to keep going. I would however, remove the Cat & replace with a D-Plate. It is not to hard to do. You do have to remove the Exhaust / Stinger section and pull out Cat. And install the D-Plate. The "water temp" lndicator lite may just be on the fritz. If the cooling water vents are flowing and engine heat seems reasonable ... Good Luck. Try PM to WFO, he is on this forum. He is still the GP1200 "Go to Guy". Steve

  3. #3
    Happily Self-Employed WFO's Avatar
    Join Date
    Nov 2005
    Houston, Texas
    Is it a GP or GPR?

    No GPR in 99

    Different motor, hulls etc

  4. #4
    She is fantastic in the water when before the panel lights up like a christmas tree! ��
    I was thinking about replacing with a D-plate, but when i look on the exploded diagrams i don't see a cat?!

    My mistake on the model, its a GPW 1999.

    I have a feeling it could be the smallest problem such as some corrosion on a connection because like i said it can run for 10 minutes some times and sometimes for an hour.

    The water that comes out the side of the hull is hot but not boiling? whats the best way ti test a sensor? but the wires and see if the problem still occurs??!!

    Thanks for the help BTW��

    Alos, i have a wire sticking out of the rear of the hull, i presume it should be wired up to a sensor of some sort, could be why the spedo docent work?... just brain storming
    Last edited by ElotLeChat; 12-09-2016 at 06:04 AM.

  5. #5
    I'd rather be jet skiing Saltwater n Premix's Avatar
    Join Date
    Jul 2010
    Fort Worth, TX
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    You will need a multi meter to test your "thermo switch" as they call it on that model.

    I found a service manual at

    The wire coming out of the rear of the hull is not attached to anything? If so, that would explain why the speedo is not working.

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