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  1. #1

    gpr1200 runs good till 3/4 throttle then loses rpms and speed at full throttle

    My gpr is losing some rpms and speed after a couple seconds of wot. I have recently cleaned the internal carb filters, removed flapper, bypassed fuel selector. Compression is 110, 106 and 107, any ideas?


  2. #2
    silver93t's Avatar
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    Immediately after it happens shut it off and pull the plugs to see what they look like.

  3. #3
    As silly as it may sound, try switching to either main or reserve (which ever it was not on when giving issue and see if that changes your result. A buddy of mine is having the same problem but it seems to resolve when the fuel selector is switched. I have had a lot of problems with fuel restriction with my primer when connected to the in...on carb 1. Since have changed it to the fuel return line instead.

  4. #4

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    How many rpms are we talking about?

    You will naturally loose a few rpms after your first hard run due to engine heat saturation to the tune of about 50 rpms. The rpms will stabilize there. For instance, if you run at 7150 rpms on your first run, it is not unusual to run at about 7100 the rest of the day.

    If you get to speed and then loose more than 100 rpms, it is possible that you are running lean and are headed for a lean seizure.

    If you want to check your plugs to see if you are running lean, then your boat must be moving at max speed, then you must kill your engine all the while holding the throttle wide open. (You need a lot of wide open smooth water to do this test). Then pull your plugs and check them.

    You really must use a good aftermarket tac to run this test to get solid numbers.

    This is a worst case scenario, and I strongly suggest that you look at this real hard if you loose a lot of rpms.

  5. #5
    I know its probably getting starved on fuel, I am just wondering where else I can look other then the things I have already done.

  6. #6
    elmatta's Avatar
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    Check your valves to see if they're opening up at at full throttle

  7. #7
    How do I go about checking that valves at full throttle?

  8. #8
    elmatta's Avatar
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    Test the valve servomotor by either pressing the start button without starting the engine or disconnecting the servomotor and reconnecting it. It should cycle once then set itself in its default position.

    Do you have waveeaters? Are you premixing? How many hours? When have you last rebuilt carbs? Any gas or oil on the bottom of the hull?

  9. #9
    Yes have the clips, 121 hours, just cleaned the carbs and filters in the carbs, not premixing I got the oil line kit and clamps from island racing.

  10. #10
    YudLuz2's Avatar
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    You could pull the head and take pictures of each piston. That would give us a idea if one cylinder is running leaner than the others. It would also be good to take a picture of the head.

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