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  1. #1
    ripcuda's Avatar
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    SLT750 - water in the engine - from towing?

    Hey Gang,
    I've read all the warnings about towing a jetski and how water can get into the engine. But has this actually happened to anyone here personally? I've always wondered how fast the tow would have to be to actually pressurize the coolant system. And how long it would have to be for the small exhaust injector to fill up the waterbox and back-flood into the engine.

    My neighbor, whose SLT 750 I rebuilt a few years ago, mentioned to me this past summer that his ski had shut-off on him unexpectedly a few times. Well... forward a month and I finally have time to take a look at it and it has water in the engine. The plugs show signs of water... so I pulled the heads and a small puddle was on the center piston. And the crank is seized up (jetpump removed). So doom on this SLT sadly. I reported my findings and asked him more about the last time it ran and he said it shut-off unexpectedly again and was towed back to his dock from across the lake... less than 1/2 mile... where it's sat since then. I'm can't imagine it was towed that fast.

    Thus my wonderings about if that short of a tow could have caused the water in the engine. Curious of others experiences.

    Cheers!


  2. #2
    Click avatar for tech links/info K447's Avatar
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    I have seen multiple water flooded engines after towing, but have not experimented with how much towing was required to begin the flooding.

    The exhaust system can already have water in it from the running engine, so the water from towing gets added to what is in there already.

    Sometimes there is more to the story, like the hull was rolled over during or prior to the tow. If it was trailered after the engine failed with a full waterbox the water can slosh around and perhaps reach the engine.

    If it sits for long enough with a very wet exhaust some of the water can evaporate and then condense inside the engine.

  3. #3
    BlueFishCrisis's Avatar
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    He also could have had a head gasket leak or multiples even. This would cause a poor running motor and may even cause the motor to stop running. Towing could continue to push water past the head gaskets (in theory).......

    Keep in mind we are talking about towing at speed or "on plane". I don't see how a tow at or just above idle would ever be an issue....

  4. #4
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    when towing, water is going thru the jet pump and some of it ( depending on how fast you are being towed) will start making it's way into the cooling system. Without the engine running to blow the water out, at some point ( if the speed is fast enough and long enough) the water will reach the top of the exhaust and flood the engine with water.

    simple fix is to pinch off the line going from the pump to the water inlet on the motor. on lots of seadoos there is a band of red tape on the line to be pinched off.

    I get several victims of this a year and they always deny going more than "five knots" ( I know better, and have seen some pretty fast towing at the lake)

    One of my customers tows his ski often at 25 knots to his secret party spot, but his cooling system is closed off to lake water.

    I'd say a half mile tow at 10 knots or faster could be a problem.
    Last edited by K447; 10-20-2016 at 09:50 AM.

  5. #5

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    My 780SLX was towed by a friend (I wasn't there, but I'm told it was "slow")... I've since run my ski and I see no signs of issues (compression is >120 per cyl). Can I assume the tow did no harm?

  6. #6
    ripcuda's Avatar
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    If you successfully started and run the engine after the tow, it's safe to assume there was no issues caused.

    My SLT was once fully submerged... rolled over with seat not latched... entire engine compartment full of water above the engine. The water was drained and the engine was brought back to running within 20 mins... and that SLT is still running great to this day.

    My neighbors SLT I describe in the first post here, sadly somehow got water into the engine then was left sitting having never re-started it... for over a month. So the water in the engine ate the crank bearings... seized it up.

    Getting an engine running after a possible water ingestion will remove any water in the engine and the internals will again get coated in oil from running (preventing rusting). If you suffered a flooded hull... there are other areas to also check where water could have gotten... flywheel stator area, ebox, fuel/oil tanks.

    Cheers!

  7. #7
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    outside of the humiliation your ski suffered while being towed, the above advice is on point..a little extra fogging oil for the winter will not be wasted money.( when the neighbors come out..you've got it right)

  8. #8
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by ripcuda View Post
    ... The water was drained and the engine was brought back to running within 20 mins... and that SLT is still running great to this day.

    ...
    For others who may be reading this later, once the water flooded engine is cleared of enough water to get it running, the next step is to immediately take it to the lake and ride it around, at speed. The engine heat and air flow (it is a 2-stroke, so all the engine intake air flows through the crankcase) from running the engine cooks away the remaining moisture and gives the engine oil a chance to re-coat everything in the crankcase.

    Just idling the engine on the trailer may not be enough. Not enough heat or air flow, and since trailer run time is limited to two minutes maximum (jet pump seals can overheat if run longer) not enough time to fully dry out the engine.

    After a good ride and several exhaust clearing blips on the trailer, fogging oil sprayed into the engine air intakes at idle will reduce the risk of rusting during storage. Then shut it down. Done.

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  10. #9

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    Ripcuda- thanks... I've just posted another thread in this forum re: electrical or fuel issue... given water can get into/near the stator, perhaps that's what killed my stator ground wire. A friend was riding my ski, flipped it, got water in the hull, tried to re-start and *FIRE*. Had to replace the stator and wires. Of course, the battery was also not properly connected, so that could have been it. I was not there to witness any of this. Thanks for perhaps helping me to solve my mystery. My ski now quits running when I peg the throttle, hence my electric vs fuel question...

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