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  1. #1

    SL750 Problems, please help a guy out!

    Ok I bought my 94 SL 750 last Summer, updates the fuel system, replaced CDI box, learned a lot, broke a lot and burned up a motor in hindsight hooking up the water line to the engine would have been easier than buying a new motor… oh well.
    Well in the off season I got a rebuilt motor and decided the name of the game this year will be patience.
    After getting the new motor in chasing down wiring issues and getting it on the lake… it seems like I’m no closer to having it running at the top of its game than I was this time last summer. I don’t have an alignment tool nor does my local shop. I can’t buy a $200 tool, when the pump went back on it slipped into the PTO coupler with no effort at all and bolted up like it always has (yes I know that doesn’t mean anything but it makes me feel better) I took it out Saturday to get some break-in done on it.
    Well It starts right up no problems (victory is mine!.... ya right) following the SBT break in I putted around at 20% throttle for 30 mins, Cooled 30 mins, then 30% throttle (yippee!) for 30, then cool 30 mins, then burst up to about 90% constantly varying my throttle position for another 30 mins.
    After the last little 30 min ride being easy on it brought it in and opened the seat…. There’s water up to the bottom of the drive shaft. (AHHHH flashbacks of forgetting to hook up the water line!) the previous two 30 min runs had very little water in the hull. So this is problem number 1 to quote captian jack sparrow “apparently there’s a leak”. So where should I start looking for this problem and how to fix it.
    Second problem this one is nothing new to me, I spent half of last summer chasing this problem down. If you give it anymore than about ¼ throttle from a standstill it dies, no stutter no hesitation just dies. And pulling the choke in slightly doesn’t help at all. The carbs haven’t been cleaned since last year (im doing that tonight) and they were rebuilt 2 years ago, I took the reeds out during the motor install and a few had cracks so I swapped in some spares I had from my other ski (the other nightmare). So all the reads look good but a few weren’t sealing all the way on the read cage. So where is my best bet to start chasing down this problem? Im taking the carbs off tonight to go through them and check pop off, anything I need to be looking for?
    I really need some help guys im about a thousand bucks into this rebuild and im about ready to put this thing on craigslist, I like working on stuff but I like ridding more.
    Thanks to all you guys help so far.

  2. #2

    Join Date
    Aug 2006
    With the ski on the trailer, get your garden hose out and fill the inside of the ski up with water... Slowly, and watch for leaks on the underside. Also, do not fill it up to where water can get into the engine!!

    If nothing is found there, run the engine like you would to flush it with a hose. With it running and water on, check hoses for leaks.

    You likely have a thru-hull seal that is bad, and when running in the water, it's forcing water in around the driveshaft.

  3. #3
    bowsniper's Avatar
    Join Date
    Aug 2008
    No.1 Drain plug?

    Where the steering cable goes thru the hull and the fitting for it.

    Your pitot tube is leaking or loose or broke off.

    Hull has a crack or hole in it somewhere.

    Trim motor mounting isn't tight.

    Water siphon tubes fell off fitting inside.

    Intake water hose leaking or off.

    Intake grate mounting boss is broken.

    Water hose on engine while running is pissing water.

    Big Pipe is loose and leaking..

    Cylinder heads loose.

    Water rail loose or warped a little.

    Cracked pump tunnel.

    Cracked thru hull boss on hull.

    Seal around the pump shoe is loose.(the big O-ring).

    And the base for the drain plug that's on the hull. It can get loose too.

    Thermostat housing is loose, broken or missing the o-ring in it.

    Inlet screen on big pipe is loose and leaking under pressure.

    Check the small rubber hose that feeds the front of the big pipe. see if it fell off or if its loose.

    Pitot tube fell off. water is suppose to push on the air in the line and the pressure produced indicates speed.

    If the hose is off, that water will fill the hull.

    The brass auxiliary fitting on the water rail is for flushing. That could leak also if loose.

    Bad thru hull seals on the thru hull bearing carrier. (or whatever thats called).lol

    Bad sealing around the upper and lower parts of the hull when produced. The topsides gets glued to the bottom of the hull.

    And any gaskets that hold back the water. ie...exhaust manifold, big pipe to ext manifold, water rail...

    I never knew it could sink in so many

  4. #4
    johnsonmtz's Avatar
    Join Date
    Oct 2006
    Mt. Zion Illinois
    Without having aligned the motor I would first start looking at the thru-hull bearing. The first trip to the lake on my '94 SLT resulted in a bunch of water in the hull. I later realized the engine wasn't aligned and was forcing the bearing to flex down and ruined the drive shaft and the bearing.

    You should be able to squeeze the throttle WOT from a dead stop and take off. The situation you describe is a lean condition so it's possible there is a fuel restriction. I would rather guess you have one of the following problems:

    1) Low Speed Needles not set properly
    2) Pop-off pressure too high
    3) low speed jets too small.

    I'm going to guess the problem is most likely #1 or #2. You low speed needles should be out 1/2 turn and the pop-off should be 10PSI to 18PSI.


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