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  1. #1

    Possible 99 GP 1200 Overheat Issues

    I recently put a 98 GP 1200 pump assembly on my 99 GP 1200. Anyone ever have any issues with overheating doing this? The water inlet on the 98 GP 1200 is just a single hole that is maybe 3/8 of an inch diameter vs. the 99 GP 1200 that has many small holes for the water inlet. The head of the engine when running is around 100 degrees. I havent measured the temperature of the water from the pisser but it feels about the same as a hot cup of coffee.


  2. #2

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    Possible 99 GP 1200 Overheat Issues

    100 is not hot at all. That is only 2 degrees warmer than body temp. I don't understand what the difference is on cooling. Water enters the engine in the same place and cycles the same. The pumps should be the same too.

    Where is the water inlet(s) you are referring to?

  3. #3
    The difference I'm worried about is the amount of water entering the engine for cooling. I'm curious if I am not putting enough water through the engine because of the 98 pump on my ski vs the 99 pump with a water inlet that allows more water to travel through the engine.

    If your looking from the back of the ski, the water inlet is on the right side just downstream from the impeller.

  4. #4
    Yamaha artisan Cutlass's Avatar
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    I think there is an early and late version of the pump vein/stator. The one most of us have is the cast in boss with a pressed in hose fitting. But there is also a bolt on block/fitting version also. Not sure when they changed it or what because I've seen 99s with the old style. Here's some pics

    Cast in fitting


    Bolt on block/fitting
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    Yamaha artisan Cutlass's Avatar
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    And I don't think there should be a problem with water flow with either one.

  6. #6

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    Possible 99 GP 1200 Overheat Issues

    Interesting. So what do u mean by "the 99 has many small holes" for the inlet.

    Where does your water enter the engine?

  7. #7
    Yamaha artisan Cutlass's Avatar
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    I assume that the bolt on block has small holes to screen out debris...but I'm not sure.

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