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  1. #1

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    SL750 Motor Quits on Wave Impacts

    Two year GH lurker here, really appreciate the forum and have learned a lot.

    My 95 SL750, named Cabo, with rebuilt carbs and triple output fuel pump has been running fine until 2 weeks ago. Was running in Pacific on medium chop day. On way out Cabo worked great but on way back, when at WOT, the motor would stop when it hit into the face of a wave. Seemed like that impact would do something. Cabo would coast for 3 seconds or so then restart and get going again. Weird.

    At medium speed, no problem. Got back to harbor and ran at WOT for 10 seconds or so against dock - no problem.

    Got home and noticed some (the normal amount) of water in the bilge. Rinsed and cleaned things and began scratching my head - what's up.

    Then 2 days ago I took Cabo out again and had no problems, zero. It ran great.

    My first thought goes towards the stator but then would the ski run great with a bad stator?

    Any ideas Hulksters?

    Thanks!


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    My initial suspicions would be the electrical, possibly in the grounding. The blue Fuji engines do not directly ground the engine to the battery. Instead the battery negative cable goes to the rear engine support bed plate. From there the plate is bolted to the bottom of the engine with some large bolts. If those bolts become corroded or loose then the electrical ground will come and go, possibly with engine vibration or hull impact causing the engine mounts to flex.

    One solution is to relocate the engine end of the battery negative cable to one of the PTO intake manifold studs. Another possibility is to use a longer battery ground cable and run the cable to one of the starter motor mounting bolts.

    Also look inside the electrical box for water or loose/corroded connections.

  3. #3
    BlueFishCrisis's Avatar
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    Something else to think about.......I have experienced this while accidentally hitting the stop button just from being thrown forward when hitting a wave. Any flailing body part tapping the stop button can be enough to shut her down......

  4. #4
    ripcuda's Avatar
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    My old SLT 750 will also sometimes cut-out upon particularly hard wake jump landings. It's pretty rare... couple times a summer at most... and it always starts right back up and runs fine. I've always suspected the start/stop switch... but never bothered to track it any further. I've never had this happen on my "newer" SLT 750 yet... <knocks on wood>.

    Cheers!

  5. #5

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    K447, BFC, and Cuda - thanks much for the wisdom.

    I will check the engine ground into the engine plate. Running in the ocean certainly gives ample opportunity for bolt corrosion etc. But when checking the stator resistances I showed good ground from ebox black to battery cable end. Ebox was clean and dry also.

    Cuda, Don't think I was hitting the stop button as my motor just 'paused' for the 3 seconds or so and it coasted. After the 3 seconds it started running again and would get up to full speed again as per normal, until the next wake impact.

    Thanks!

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by pajones View Post
    ... when checking the stator resistances I showed good ground from ebox black to battery cable end. Ebox was clean and dry also.

    ... my motor just 'paused' for the 3 seconds or so and it coasted. After the 3 seconds it started running again and would get up to full speed again as per normal, until the next wake impact...
    Does this "pause" occur at the instant of the wave impact, or a few seconds later?

    It sounds like the engine may be continuing to run during the pause, but on only one or two cylinders. This would feel like a sudden power loss, especially if you were running at speed at the time. Then when the other cylinders come back to life the engine power resumes.

    Electrical ground issues can be tricky to track down, especially when they only happen intermittently. A wave impact can cause things to shift, stress and flex which otherwise can test as electrically 'good'.

  7. #7

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    K447,

    The pause happens right when the hulk hits the wave. It seems like the whole motor cuts out as if I'd released the throttle. I don't think I hear even one cylinder going when it happens. I think it has to do with the seawater in the bilge sloshing up and about upon wave impact as it happened late in the session when there was a little (1" deep) water in the bilge areas.

    I'll check the main ground connect and try to recreate the fault this weekend if I can get out.

    Thanks

  8. #8
    LaveyT's Avatar
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    Interesting, It may be worth running a 2000rpm or so on the trailer in the water and tapping with a mallet (no ball peen hammers) around the start stop switch. just curious what the shaking would do.
    I would suspect a grounding issue.

  9. #9
    BlueFishCrisis's Avatar
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    So you are saying you don't have to restart the motor, that it just loses power then regains it all by itself? If that's the case, doesn't sound like a start/stop switch issue. Along with checking the grounds, I would be looking at plug wires, plug boots, and spark plugs for damage as well. If the boots aren't pushed on all the way, you can get intermittent contact. If a plug is damaged, it can cause intermittent fire, same with damage to a plug wire causing a ground condition and temporarily losing spark.

  10. #10

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    If this is an SLT with the individual fuel lines in the tank that hang freely as opposed to the aluminum pickup tube, could this also be a fuel delivery issue?

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