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How to check coils on 1986 110 Johnson

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  • How to check coils on 1986 110 Johnson

    How do I check each of the coils on my 110 Johnson? I put in new plugs, but still have a miss.

  • #2
    Re: How to check coils on 1986 110 Johnson

    Ted, Try here: web page

    "Boating is Life...All the rest is just Details"

    2007 Bentley 200 Cruise
    2007 Merc. 90 4 stroke


    • #3
      Re: How to check coils on 1986 110 Johnson

      Use a simple 1.5 volt flashlight battery on the primary (connection where the coil and points are connected) and ground (or as the case of a solid state module, the coil primary lead from that module.) Polarity doesn't matter but always disconnect the coil from the module to prevent damage to the module. As you flash the correct connection to the flashlight battery the secondary of the coil should produce a consistent though weak arc on the spark plug gap. Remember your using 1.5 V and not the strong magnets of the flywheel to excite the coil. Compare the strength of the arc to that of a known good coil or to others on multi-coil motors. If a tested coil falls short in a comparison, replace. Be careful or you will get shocked. If you attempt to do the test with the points still connected you will have to make sure the points are open and remember the condensor is still in the circiut so another possible cause of loss of spark. Most of the time the primary of the coil can be disconnected easily from the motor while leaving the secondary and spark plug connections intact for this test. Ron


      • #4
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        Re: How to check coils on 1986 110 Johnson

        Ted - I would try to isolate the cylinder that is giving you the problem by starting the motor and pulling a sparkplug at a time. Even better use a spark tester and check the color of the spark and how far the spark jumps - should be at least 1/2".When you find the one that is weak or dosen't fire then switch a coil from a good cyl to the one you suspect. That should give you a good indication