Seadoo 951 carb intermittently dies/shuts off
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  1. #1
    PWCToday Regular
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    Seadoo 951 carb intermittently dies/shuts off

    A little backround, 2000 carbed 951, fuel lines changed. Fuel valve, main filter/bowl, and internal carb filters cleaned.
    Opened mag cover and didn't see any broken gear/teeth from bendix floating around causing a short to the stator. All fuses good.
    Idling and midrange throttle runs good, no hesitation, no bog, nothing, then at full throttle "sometimes" it'll just shut off. It starts back up, runs fine again. Idles at 2900 on trailer and about 1400 in water. When it does not shut off, it will rev to 6800-6900rpm. What could be causing this?

  2. #2
    PWCToday.com Is My Home Away From Home Matt Braley's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Possibly a bad DESS post or a bad key. If the start/stop button or the wiring to it fails it can shut off randomly also.

  3. #3
    Frequent Poster mrwhipper's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Quote Originally Posted by Matt Braley View Post
    Possibly a bad DESS post or a bad key. If the start/stop button or the wiring to it fails it can shut off randomly also.
    +1

    If all that tests out, it's a long shot but try and run with the gas cap off. Just in case the check valve is stuck.

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    PWCToday.com Is My Home Away From Home Chester's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Check your compression. It might be seizing. Remove the RAVE valves and look at the pistons.

    Chester
    Speed is very expensive. How fast do you want to spend?

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  5. #5
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Quote Originally Posted by Chester View Post
    Check your compression. It might be seizing. Remove the RAVE valves and look at the pistons.

    Chester
    if it is shutting down wouldn't it have to be extremely lean? Slightly lean would seize it without warning

  6. #6
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    When the motor "shuts down" it is seizing a piston 99% of the time.

  7. #7
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Quote Originally Posted by Spades View Post
    if it is shutting down wouldn't it have to be extremely lean? Slightly lean would seize it without warning
    An engine will commonly seize on a wide open throttle run, then restart
    almost immediately. The first time it happened to me, I thought it
    ran out of gas. So I switched it to reserve and restarted it.

    Now that I have more experience, I know that a days worth of riding
    is not worth it, and to pull it out of the water to inspect the engine.

    I try to recommend that people recognize a potential problem when
    it occurs, and to play it safe. Most of all, do not rationalize away
    your problem by telling yourself that if you baby the engine, it will
    last for the rest of the day.

    When the GSX Limited first came out, brand new 951's were seizing
    and breaking piston skirts. It was caused by water ingestion, because
    the airbox was sucking water off the bottom of the hull and into the
    carburetors.

    It is a problem on all watercraft. The damage caused by water ingestion
    can look like wide vertical lines along the intake & exhaust skirt. It resembles
    a grove cut by your thumbnail vertically along a wax candle.

    The water damage decreases the area of the piston can hold oil, and
    the piston will seize. The skirts tend to turn a dirty gray color, and can
    melt the piston crown and expose the rings until they snag the exhaust
    port.

    When the engine seizes the first couple times, it may not affect the
    compression test. That is why small changes of 5 psi can be significant,
    and at least on the 785, and 951 you can remove the RAVE valves to
    inspect the piston. (Rust damage is another source of small losses in
    compression).

    Another funny characteristic is that nearly all the damage occurs on
    the piston. In the early stages the cylinder is nearly untouched. That
    is, until it seizes and leaves aluminum smeared on the cylinder wall.

    There are other ways to seize and melt a piston without the jetting
    or the fuel pump being the direct cause. Often jetting is lean because
    of the load on the engine is greater do to mismatched accessories and
    modifications, but this is more common on 580 to 785's, Kawasaki's
    and Yamaha's.


    Bill M.
    Last edited by wmazz; 10-23-2018 at 05:14 AM.
    Horsepower == Speed, RPM != Speed



  8. #8
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Quote Originally Posted by pwc enthusiast View Post
    When it does not shut off, it will rev to 6800-6900rpm. What could be causing this?
    Are you saying the engine runs away??

    If so, I have found that a leaking carb base gasket is the common cause.

    Did you reuse the carb base gaskets?? Your out of the water idle seems a
    bit high.


    Bill M.
    Last edited by wmazz; 10-23-2018 at 05:25 AM.
    Horsepower == Speed, RPM != Speed



  9. #9
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Quote Originally Posted by wmazz View Post
    Are you saying the engine runs away??

    If so, I have found that a leaking carb base gasket is the common cause.

    Did you reuse the carb base gaskets?? Your out of the water idle seems a
    bit high.


    Bill M.
    The engine does not run away on the trailer. Not once did it even almost run away.

    I meant when it revved to 6840rpm it was in the water, and only for 3 seconds, after that it shut off and started back up. It didnt shut off immediately, I brought it back to midrange and then it randomly shut off. Had a feeling something's up so I idled back to my trailer to save my engine. Compression is 120psi each.

    If it is seizing, what could it be? Both accel pumps squirting a strong stream, r&d filter, 80g springs, 87.5 lows (1.5 turns out), 165 highs closed, stock 2.0 n/s. I did reuse the carb base gasket, they were new and only used for 4 two hour rides at most.

    Any help appreciated. Thanks.
    Last edited by pwc enthusiast; 10-23-2018 at 07:06 AM.

  10. #10
    Resident Guru SURFnTURF's Avatar
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    Re: Seadoo 951 carb intermittently dies/shuts off

    Its lean on the high speed circuit just a little due to the r&d filter.
    Open the adjusting screws 1/4 turn,check the pop off, you want them to be no more than 20psi
    951s dont like being slightly lean when revs are being held back due to prop pitch or pump pressure too high
    That engine with an impeller pitched correctly should be spinning over 7000rpm even with 120psi.
    I would ditch the pumps on the carbs and run 95 lows as well as the 951 loves a lot of fuel mid range,this will make it a lot more responsive

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