Thread: Pencil Coils

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  1. #1
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    Pencil Coils

    Don,

    I have a 2006 Mercury Verado 275 HP serial #1B301246.

    Back in 2012 the dealer replaced all 6 of the pencil coils. Mercury relations picked up the tab for 2 of the 6 and I paid for the other 4. Since then I have only put 49 hours on the motor.

    The first time I took it out this year, I could not get it on plane. The RPM's would go up to around 3500 the motor would shudder and RPM's drop to around 3000. Tried multiple times and the same thing kept happening. Similar to the symptoms I had back in 2012.

    Took it in for service. The Verado Certified mechanic hooked up the computer and tested each pencil coil but all showed good. He was not able to test under load as if it were on the boat. When he pulled the coil from the bottom plug he noticed some moisture when he tapped it on his hand. He could not determine where the water had come from.

    I purchased a new pencil coil and put it in the bottom plug where the technician found the water. First time out I was on plane in about 3 seconds without any hesitation. Started and stopped about a dozen times and it ran just the way it should. Looks like the coil failed under load.

    The question I have: is there any way to test the coil to determine if it is good or bad other than under load?

    Thanks in advance for the help
    John

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Pencil coils are tested via an Enclosed/Spark-arresting SPARK TESTER, with a 7/16" gap, and the Computer Diagnostic System.

    Did you happen to change the SPARK PLUGS? We often find misfires or down on power at #5 or #6 to be caused by spark plugs that need to be replaced (may or may not "appear" that way).


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  3. Member
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    #3
    Don,
    Thanks for the quick response and information.

    The plugs were changed when the 6 new pencil coils were replaced which was 49 hours ago. Just to eliminate them as a source of the current problem, I had them all replaced. I still had the same problem after that and it was not until I put the new pencil coil on the bottom plug that the problem went away.

    Appreciate your help

    John

  4. Member
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    #4
    Check ohms on all combinations of the terminals on all coils. Compare results to find the bad one.
    2012 Bass Cat Cougar FTD
    2012 Mercury ProXS 250 w/ Fury 3 26

  5. Member
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    Pismo Beach
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    #5
    Having A similar issue with my 300. Replaced all the plugs, ran great for about a hour then right back to the same issues. Gonna due all the coils and plugs and see if that’s it. $65,000 for boat and engine package and I got to deal with this bullshit!!

  6. Member
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    #6
    Can't say for OPs Verado, but most other Mercury outboards have an hours or frequency (usually annual or higher) replacement interval and suspect that's why Don inquired about the plugs. They may only have 49hrs but are 9yrs old.
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    Phil
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