Results 1 to 6 of 6
  1. #1
    Member
    Join Date
    Sep 2010
    Location
    NW Georgia
    Posts
    32,810

    Testing coil with timing light question

    Mercury 175 ProXS
    SN 1B537766
    Year 2008
    running 23 pitch Tempest @ 5800-6,000 rpm

    Running along and immediately went to 5100-5200 rpm, them a little later went back to 5800-6000.
    Then went back to 5200 and never “kicked” back in. The last time the engine acted like this the merc mechanic found dead coil.

    My question is do you clip the red on timing light on positive on starting battery and the neg of light onto coil wire going to the plug? The mechanic told me how to check it myself but I have forgotten with the light hooked up. I think Don Weed mentioned this once but I didn’t find it.

    Thanks guys/folks ahead of time.
    Praying for a Cure

  2. Member lpugh's Avatar
    Join Date
    May 2009
    Location
    Sacramento Ca
    Posts
    5,164
    #2
    red and black leads go to pos & neg battery source, can be hooked to appropriate locations on such as slave solonoid and engine ground. Inductive lead on plug wires one at a time if the light does not flash on wire there is a good possibility of coil failure on that cylinder, just be aware there are other things that could cause this as well. Also even though it does flash there is still a possibility that the coil can not develop all the voltage that it is designed to. Still a very good quick test
    Thank You Leon Pugh

  3. Member
    Join Date
    Sep 2010
    Location
    NW Georgia
    Posts
    32,810
    #3
    One coil no fire at all, just like the last time the mechanic showed me. Does anything in particular cause them to go bad?
    Praying for a Cure

  4. Member lpugh's Avatar
    Join Date
    May 2009
    Location
    Sacramento Ca
    Posts
    5,164
    #4
    Some had issues I believe and should have all of them updated. An open plug wire can cause premature coil failure, check continuity of all the wires just to be on the safe side
    Thank You Leon Pugh

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
    Join Date
    Apr 2008
    Location
    Greenville, SC (US)
    Posts
    94,945
    #5
    Quote Originally Posted by wildturkey View Post
    One coil no fire at all, just like the last time the mechanic showed me. Does anything in particular cause them to go bad?
    Swap with another coil. No flash does NOT always mean a bad coil... a bad plug wire, spark plug, etc. are also possible.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

  6. Member
    Join Date
    Sep 2010
    Location
    NW Georgia
    Posts
    32,810
    #6
    Thank you all for input. Ended up coil. Least it wasn’t worse.
    Praying for a Cure