New to Jet Skis. Engine problem. Need some guidance.
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  1. #1
    PWCToday Newbie
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    New to Jet Skis. Engine problem. Need some guidance.

    New to jet skis, but not new to 2 strokes. Bought the ski recently from a local, wealthy family. The ski had been sitting indoors for a long time. I believe the last registration was 10 years ago.

    Need help with 2 issues:
    1) 2 stroke oil shooting out the spark plug hole of #1 cylinder. How do I approach fixing this. Only coming out of cylinder #1.

    2) very weak spark. I have one of those inline lights and the light is VERY weak. Just barely starts to show the lightest ignition of the bulb in the tester. What do I start checking to diagnose the problem?

    By the way, I do see the gray fuel lines have been replaced.

    Thanks for any help and guidance you can provide.

  2. #2
    I dream skis
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    Re: New to Jet Skis. Engine problem. Need some guidance.

    We need a starting point... Did you inquire if it had been properly prepared for storage before that 10 year retirement? i.e.. fuel drained and run from carbs. engine fogged with oil, water drained from water jackets, etc

    1) What model ski/engine is it?

    2) What led up to you seeing the oil shooting out of the hole? Did you try to start it right away when you got it or were you checking it out prior to starting attempting to start it? The oil you see could be remnants from fogging the engine?

    3) if you are trying to start it, put premix in the tank until you verify the oil injector pump and lines are in good working order.

    4) Do a compression check.
    2, 1998 TS 770 L, restored and running great as of July 2019 (NO THANKS to the person at SBT, who put the WRONG crankshaft bearing into the rebuilt engine I got from them)

  3. #3
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    Re: New to Jet Skis. Engine problem. Need some guidance.

    hemmjo, answers to your questions.

    1) 97 GTX. 787 engine
    2) I pulled the plugs to check compression. 2 stroke oil from the ski oil tank is coming out of cylinder 1. LARGE amounts. It is not fogging oil.

    What are the potential sources for the 2 stroke oil seeping into the crank case?

  4. #4
    I dream skis
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    Re: New to Jet Skis. Engine problem. Need some guidance.

    I am just guessing here.

    Is it possible while sitting for 10 years, the oil leaked through the injector pump and collect in the crankcase of that cylinder. 10 years is a long time, 3650 days. 1 drop per day would add up 8oz of oil in 10 years. It does not take much oil to make a mess. The oil tank sits higher than the engine. Gravity is a constant force, trying to pull stuff down.

    Once again to be clear this is just a guess, but it seems to me it is the only source.
    Last edited by hemmjo; 10-19-2021 at 07:34 AM.
    2, 1998 TS 770 L, restored and running great as of July 2019 (NO THANKS to the person at SBT, who put the WRONG crankshaft bearing into the rebuilt engine I got from them)

  5. #5
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: New to Jet Skis. Engine problem. Need some guidance.

    Leaking inner main seals on older SeaDoo's is fairly common.

    I believe "Myself" has a work around for that.

    After you get the oil out of the bottom end, try checking the
    spark with non-resistor equivalent of the NGK B8ES spark plugs.


    Bill M.

    I would plan on at least inspect/rebuild the carbs, after 10yrs I would
    suspect the float diaphragms, and the O-ring on the seat will need to
    be replaced. The O-rings on the hi and lo screws too.

    For best results use the oem Mikuni rebuild kit, and needle & seats.
    Last edited by wmazz; 10-19-2021 at 02:21 PM.
    Horsepower == Speed, RPM != Speed



  6. #6
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: New to Jet Skis. Engine problem. Need some guidance.

    Quote Originally Posted by wmazz View Post
    Leaking inner main seals on older SeaDoo's is fairly common.

    I believe "Myself" has a work around for that.
    Yes I do. I sure didn't come up with it but I have done it many times. I should do a write up with pics and we could have a mod make it a 'sticky'.

    First things first......pinch off the 1/2" line coming from the oil tank down under the carbs.
    Crank the oil out of the cylinders. Crank maybe 30 seconds then let the starter cool down for 5-10 minutes.
    Leave the fuel switch off!
    Get a can of fogging oil.
    Spray a little fogging oil in each cylinder and reinstall the spark plugs.
    Hold throttle 1/4 open and try starting it.
    It might spit and stop turning.......it pulled more oil up and hydrolocked.
    Remove plugs, crank a bit more oil out, spray a bit of fogging oil, replace plugs, hold throttle 1/4 open, try again.
    ........rinse and repeat......
    Don't do this in the garage......place a cardboard box full of paper towels or newspaper under the rear of the ski.......when it fires off it WILL puke a big nasty mess out of the exhaust!!!
    Once it actually starts easily and idles you can do a compression check.
    If the compression check is good (145-165psi) You can start going through everything.....carbs, jet pump, etc.
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