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  1. #1

    Join Date
    Oct 2021
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    1997 GTX Bogging seems unsolvable

    Hey guys, long time lurker and just joined. Awesome community.

    Got a headscratcher

    Just picked up a 1997 GTX 787 twin carb with new engine installed (has paperwork to back it up but does not specifically say what was replaced.

    Bogging/won't rev up much past 3500 RPM, on land or in water no real change. 2 mph in water. Starts right up and idles nice (3000 rpm on land, 1500 in water)

    150 psi in both cylinders, I have rebuilt the carbs with real mikuni kits (set carbs to seadoo specs, correct pop off pressure, all jets clean and clear) and replaced all fuel/oil lines and filters. I installed a new rectifier as well - ski is now making perfect voltage and no AC voltage (was kinda high before but did not affect issue)

    I tried adjusting low speed needle in 1 turn and out 1 turn in increments of 1/4 turns to see no real changes

    Also has new plugs, good gas and good oil.

    Does this sound like RAVE valves?

    Any ideas appreciated, hopefully pics work
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  2. #2

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    Fuel Supply?

  3. #3

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    Oct 2021
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    I have fuel to the carbs, primed the system with compressed air and I assume the pulse pump is working because it idles fine and won't cut out.

    Also, pulling the choke kills it so I don't think I am lean. But I am not a rotax expert

  4. #4
    Pacer's Avatar
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    Change the fuel selector valve.

  5. #5
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Have a look at the water box regulator and check the raves on the engine too

    The water box regulator often had a small hole in its diaphragm from the spring clip

    Rave valves west and get gummed up

    A “new” engine should have this checked since they spent what I think was too much time on paint

  6. #6

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    Oct 2021
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    Quote Originally Posted by Pacer View Post
    Change the fuel selector valve.
    Forgot to mention I replaced that as well

  7. #7

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    Oct 2021
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    Nmpeter, I will check out the water and rave valves tonight.

    How could the water valve cause a bogging issue? (Again I'm not a rotax guy)

    Thanks!

  8. #8
    Myself's Avatar
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    Bad plug wire or boot.....ohm them out. 3500rpm is exactly half of what that engine can turn, Sounds like it's only hitting on one cylinder to me. Have you tried to start it up on only one cylinder with the other plug wire off? Try both.

  9. +1 by:


  10. #9

    Join Date
    Oct 2021
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    Quote Originally Posted by Myself View Post
    Bad plug wire or boot.....ohm them out. 3500rpm is exactly half of what that engine can turn, Sounds like it's only hitting on one cylinder to me. Have you tried to start it up on only one cylinder with the other plug wire off? Try both.
    What should their resistance be? It sometimes will make it above 3500 but only while bogging/surging. Never makes it on plane. Have not tried running on one cyl I will check that.

  11. #10
    Hurricane1000's Avatar
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    I have personally seen this happening on 2 stroke Sea-Doo.

    Try running the fuel valve on reserve. The fuel pickup in the gas tank has been known to fail. By the housing cracking and not picking up fuel.
    In addition make sure the crankcase nipple is firmly attached with a clamp. Wire ties leak, causing air leak.

    Good luck.

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