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  1. #1
    PWCToday Newbie
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    DESS vs Non-DESS MEPMs ?

    Hey Folks,

    Currently building out a couple older skis and had a question about MEPM differences.

    I believe sometime around 96', seadoo switched to the DESS system. Are there significant differences between older mepms and newer mepms for 587-717 motors.

    I'm currently swapping a 657x motor into an older ski and have the following mepms:

    2 - 94 sp mepms
    1 - 96 GTI mepm w/dess

    Are the ignition curves different between the older and newer mepms? Would it be worth running the newer mepm w/dess? I would prefer not to use dess system out of simplicity but if there is performance to be gained, I don't want to pass it up.

    Thanks....

  2. #2
    PWCToday Regular DanSquires's Avatar
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    Re: DESS vs Non-DESS MEPMs ?

    this is not going to work... you simply need the electronics from a 94 XP.
    There are other models that came with a 657X, but that's the easiest to remember and search for.

  3. #3
    PWCToday Newbie
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    Re: DESS vs Non-DESS MEPMs ?

    Not sure I follow... I swapped a 717 into my 95' Sportster and that boat was originally powered by a 657x, I used all of the stock 657x Sportster electronics. Both motors had 4 wire stators...

    So, why won't a 717 mepm work for a 657x? Building this thing from the ground up... Will have the stator and everything from the 96 717 gti...

    If someone knowledgeable could give some insight about the differences between DESS and Non-DESS MEPMS that would be great.

  4. #4
    Resident Guru hafweigthr's Avatar
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    Re: DESS vs Non-DESS MEPMs ?

    It depends on what ski the 657X motor is from. A 1994XP motor had a 5 wire stator which will only work with the 94 XP electronics. 95 GTX and 95 SPX 657X typically had the 657X 4 wire stator version but not always. If you interchange the flywheel and stator for a 4 wire then it will work. A 717 and a 657 should be directly interchangeable since both have the 4 wire stator. The only functional connections from the 657 and 717 motors(besides temp sensor) are the stator connections and the 2 plug wires.

    A 94 -SP MPEM is for a 587 motor which will have a different rev limiter setting. 96 GTI MPEM is your best bet as long as the 657X has a 4 wire stator and flywheel.
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  5. #5
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: DESS vs Non-DESS MEPMs ?

    If they are both 4 wire stators they you are fine.

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