No Spark Merc 40hp 4-Cyl 1991

Discussion in 'Outboards' started by toadmiller, Aug 4, 2014.

  1. toadmiller
    Joined: Aug 2014
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Hampshire

    toadmiller New Member

    Greetings, new member question here...

    I have what I "think" is a 1991 Mercury 40hp 4-Cyl 2-stroke (oil injected) motor. Trouble symptoms began as motor would suddenly go from full, normal power to loss of approx. 80 power. Then, intermittently it would cut back to full power, run for a few hours, then back to 20%. Suddenly, yesterday it instantly quit completely. When it quit, it was instant no spark, not a surging-type failure as when you run out of gas.

    I tested all coils, they were fine. I am guessing it's something in the Powerpack (?) but I am not up to speed on these engines beyond that. Any suggestions on diagnosis before I start throwing expensive parts at it by guessing?

    Thanks to all for any advice you might offer!

    -Todd
     
  2. powerabout
    Joined: Nov 2007
    Posts: 2,925
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    The kill circuit, its magneto ignition so the key circuit shorts it to ground
    When you have no spark its the first thing to check.
    Black yellow wire.
     
  3. toadmiller
    Joined: Aug 2014
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Hampshire

    toadmiller New Member

    Thanks!

    OK, thank you for the suggestion. Interestingly, the key switch "warning beep" started coming on for no reasons in recent weeks. I would have to back off the ignition key (i.e. turn it slightly counter-clockwise) to get it to stop screaming. Maybe related?
     

  4. powerabout
    Joined: Nov 2007
    Posts: 2,925
    Likes: 66, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    You might be turning off the power to the horn but not stopping the engine.
    You might want to look into that horn issue first
     
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