15-hp Merc with CDI

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  • retiredoz

    US Member - 1 Year
    Replies: 534
    Topics: 26
    #5337

    Friend is fighting an ’88 15-hp Merc (ES), it fired up, ran briefly, and idled to a stop, apparently never to run again. No spark on either cylinder.
    Other than the kill switch, is there a component that is failure-prone ? Besides the magic box ?


    outbdnut2

    US Member - 2 Years
    Replies: 1666
    Topics: 84
    #44626

    I repaired a 9.9 Merc that uses the same ignition module that’s on the 15 you have a couple years ago – someone at this site gave me a simple Ohm-meter procedure for checking out the module and it quickly showed me it was bad – I can’t find what I did with that procedure – maybe someone will post it for you. I remember replacing it with an aftermarket Mallory module I found online that was a lot cheaper than Mercury or Sierra. Mallory is a very respected name in performance automobile ignition systems.
    Your problem could be the module, or the stator that’s under the flywheel.
    Dave


    retiredoz

    US Member - 1 Year
    Replies: 534
    Topics: 26
    #44628

    Thanks. I was hoping somebody would tell me the under-flywheel coils could be the problem, but I bet they break less often than the module. The testing procedures I found are for a motor a bit older, and I don’t trust the Merc fiends not to change the color coding of the wires.


    outbdnut2

    US Member - 2 Years
    Replies: 1666
    Topics: 84
    #44640

    Hey – I found that I had saved the test procedure in my computer – here’s copy and paste of it below:
    Dave

    I’ll bet it’s the switchbox. Hopefully the stator is still ok after you turned the motor over with the leads disconnected.
    Test the trigger (brown/white and brown/yellow leads) between the leads with ohmeter at Rx100 scale. Should read 6.5-8.5.
    Test the stator (black/white and black/yellow leads)
    first test stator plate to ground, reading should be 0. You may or may not have a black ground wire from the plate to block, some used the stator base as a ground to block. Test between the black/white lead and ground with ohmeter at Rx10 scale, should be 12-18. Test between black/yellow and ground, meter at Rx1000 scale, should read 3.2-3.8. Test between black/yellow and black/white leads, meter at Rx1000 scale, should be 3.1-3.7.

    You can test the switchbox by using jumpers and reversing the stator leads and trigger leads before the switchbox. If the no spark moves to the other cylinder, it’s the switchbox


    jeff-register


    Replies: 1288
    Topics: 49
    #44724

    Usually when the switch box bails it is the scr. The silicone Controlled Rectifier is the big boy switching device & the trigger fails.

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