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  1. #1

    750 Bogging Mystery Problem

    94 750SLT

    Bought the ski late last year, worked a few times then bogged out on us. It runs great on the trailer but under load it bogs (maybe 7 mph at WOT). We had the carbs rebuilt, it worked for about five minutes then bogged again (carb rebuild must have been coincidence). Replaced the fuel pump and lines, replaced the inline fuel filter, still no difference. Plugs have spark but haven't been tested for strength or anything like that. This year we brought it out for another test and it worked great for about 5 minutes then back to bogging. While it bogs I believe the RPMs are around 3500, on the trailer it revs to 6000 or so (can't tell anymore as the MFD burnt out over the winter). Whatever the problem, it appears to allow the ski to run flawlessy every so often. I see from reading on here that the 750SLT does not have limp mode. Everything mechanically seems to be functioning, perhaps something in the black box is coming loose?

    No one seems be able to solve this problem yet it does appear to be somewhat common. Anyone else with a similar problem, please share your experience.


  2. #2
    Moderator beerdart's Avatar
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    Check the jetpump for binding.

  3. #3
    What do I look for if it is binding or can I find all that in the manual?

  4. #4
    Now that I think about it, the ski does seem to rattle a bit back there.

  5. #5
    Moderator beerdart's Avatar
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    Just pull the pump and inspect the bearings and impeller clearance.

  6. #6
    la90043's Avatar
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    Quote Originally Posted by Rich2009 View Post
    94 750SLT

    Bought the ski late last year, worked a few times then bogged out on us. It runs great on the trailer but under load it bogs (maybe 7 mph at WOT). We had the carbs rebuilt, it worked for about five minutes then bogged again (carb rebuild must have been coincidence). Replaced the fuel pump and lines, replaced the inline fuel filter, still no difference. Plugs have spark but haven't been tested for strength or anything like that. This year we brought it out for another test and it worked great for about 5 minutes then back to bogging. While it bogs I believe the RPMs are around 3500, on the trailer it revs to 6000 or so (can't tell anymore as the MFD burnt out over the winter). Whatever the problem, it appears to allow the ski to run flawlessy every so often. I see from reading on here that the 750SLT does not have limp mode. Everything mechanically seems to be functioning, perhaps something in the black box is coming loose?

    No one seems be able to solve this problem yet it does appear to be somewhat common. Anyone else with a similar problem, please share your experience.
    You replaced the fuel lines? How about the fuel restrictor inside the fuel return line from the carburetor rack to the fuel tank. Is the restrictor still inside there. There should be one there. Its holds fuel pressure for the Carburetors to be maintained full of fuel and have no air pockeks.

  7. #7
    la90043's Avatar
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    Do you have installed the new updated 3 outlet fuel pump huh? Is it also in its new updated location? Low inside the hull as close as possible to the pulse line block fitting?

    Do you think it might be starving of fuel because the "AIR" one way check valve is clogged/worn out/ needs replacing?

  8. #8
    It is the updated 3 port fuel pump but still mounted in the stock location. I didn't change the return fuel line so the restrictor must still be in there. Where do I find the one way check valve? The part I don't understand is why the ski has worked a few times for a few minutes. That's why I thought it may be electrical but no one has suggested anything electrical.

  9. #9
    la90043's Avatar
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    Quote Originally Posted by Rich2009 View Post
    It is the updated 3 port fuel pump but still mounted in the stock location. I didn't change the return fuel line so the restrictor must still be in there. Where do I find the one way check valve? The part I don't understand is why the ski has worked a few times for a few minutes. That's why I thought it may be electrical but no one has suggested anything electrical.
    ITS THE NO. 10 IN THIS DIAGRAM LINK.

    http://fiche.worldofpowersports.com/...pe=13&A=9&B=16

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Did you pull the jet pump and check the impeller bearings?

    Until you figure it out, unplug the MFD. See diagram below.

    Sometimes a duff MFD can cause weird problems.

    If that doesn't help, spend some time cleaning up the electrical system. Remove, clean, and re-tighten both ends of both battery cables, and both all cable connections on the start solenoid (relay).

    Next check the electrical system grounds. Should have zero ohms from black wires inside electrical box to battery negative.

    Also have a look at this;
    How to test CDI, Magneto stator coils & Ignition coils on Fuji engines
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