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  1. #1

    1996 780slt not running full power

    The ski ran great last time out and sat since Sept 2010. Took it out yesterday and it would run ok and idle ok but every time i would give it throttle it felt like being bogged. I check and cleaned my plugs but that didn't help. When I was in the water i put in reverse and gave it full throttle and it motor sounded great!! put it back on forward and it ran like a bat out of hell. After a few more minutes it was bogging again. So i suspect it's a mechanical issue with maybe the impeller. I think when i put it in reverse the back pressure pushed something back and ran well in forward until it came back off. Have never worked on a jet-ski but I am mechanically inclined. Does anyone have any thoughts on what I should be checking first. Again I'm fairly certain it's not electronic or a fuel problem but something to do with the drive.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    What maintenance has been done on this engine? Carburetors rebuilt, fuel lines replaced?

    Was the gasoline in the tank stabilized?

    You may have a binding bearing in the jet pump. Remove the jet pump and check for smooth rotation of the impeller. See my signature links for how-to and related jet pump info.

  3. #3
    Ok, so I'm stopped a bit. I removed the jet pump and shaft rod. Started the ski without the jet pump or shaft and same problem with bogging at throttle. Waited 5 minutes, started it again and problem was gone, smooth response with plenty of power. Re-assembled jet pump and greased the shaft, started it again and bogging again at full throttle. what gives ???, prior to this maintenance done was, rebuilt fuel pump, replace all fuel lines, added a see through fuel filter ( clean fuel is visible ).

    See pic below, shaft looked pretty worn. Should i replace it?


  4. #4
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Sounds like how my SL780 was running until I pulled off my spark plug boots and clipped about a 1/4" off the end and put the boots back on. It was basically running on 2 cylinders when it got warmed up.

  5. #5
    Hmm, I may just look into that. I do recall when i took to the water, removing and cleaning the plugs and that seem to work for a bit. Thanks!! I'll check it out.

  6. #6
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    I should clarify...I clipped off a quarter inch of the wire, not the boot. Not saying that you would have cut the boot, but just wanted to be sure because the way I worded it, it sounded like I was talking about the boot!!

  7. #7
    Quote Originally Posted by hyoctane23 View Post
    I should clarify...I clipped off a quarter inch of the wire, not the boot. Not saying that you would have cut the boot, but just wanted to be sure because the way I worded it, it sounded like I was talking about the boot!!
    So did you cut the actual wire or the clip that holds on to the sparkplug? If you cut the wire, did you just remove the metal clip and how do you put it back if so?

  8. #8
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    You cut the wire itself...just a quarter inch off the end, no more needed. What happens is that the wire inside gets corroded and doesn't get a good connection to the boot. The boot will twist on and off. Tip: when you screw them back on, I use a little bit of spit inside the boot so you can twist the wire on. Otherwise it is a pain in the ass to get on.

  9. #9
    Just to update. I cleaned the plug wires as they were pretty dirty. It's running great now...

  10. #10
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Meaning you clipped the wires or did something else?

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