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  1. #1
    Member
    Join Date
    Nov 2018
    Location
    Bayou, LA
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    208

    Mercury 200 HP V6 - Double Firing

    1998 Mercury 200 HP V6
    Serial #: 0G638250

    I am experiencing tach issues (reading higher rpms than actual). As a result, I decided to test the rpm of each cylinder by using a timing light with an inductive tach by clamping to each spark plug wire. The #5 and #6 wires are reading upwards of 6500 rpm at idle while the other spark plug wires show roughly 1000 rpms (using the timing light with tach) all while running on the muffs at idle.

    Are there any reccomended tests I can try to isolate the problem?

    #5 cylinder:
    20230312_151605.jpg

    #2 cylinder:
    20230312_151620.jpg
    Last edited by greauxpete; 03-12-2023 at 07:18 PM.

  2. Member
    Join Date
    Jun 2013
    Location
    LONGVIEW TEXAS
    Posts
    13,938
    #2
    preform bias system tests outlined in serv manual
    .................................................. ...the scariest thing in life is the unknown ...................................

  3. Member
    Join Date
    Nov 2018
    Location
    Bayou, LA
    Posts
    208
    #3
    Changed the coil and the problem seems to have gone away. No change after replacing both switchboxes. My dang DVA is not working with my multimeter, so I had to swap parts from the other motor to troubleshoot.