Electrical Gremlin, ECM/IAC related 8.1s

Discussion in 'Electrical Stuff' started by Zorba, Jan 19, 2018.

  1. Zorba

    Zorba Active Member

    May 21, 2008
    East Harbor, Lake Erie
    2006 340 Sundancer
    Twin 8.1 Mercruiser
    Again, i think i know the answer here but want to bounce it off you guys. At the end of the '16 season while at cruising RPM (3350) very occasionally I would lose about 500-600 rpm my gauges and vessel view would lose contact with the starboard motor. The RPM loss was very quick, just a hiccup and the gauges and vessel view would recover soon after. Perplexed i thought the RPM loss was related to the IAC so i changed that. Problem solved for the remainder of the '16 season. no further issues.

    Fast forward to summer of '17. first half of summer no issues, boat runs great. On a 50 mile cruise, I get same symptoms, but this time when i lose rpm i hear 1 chirp from dash and lose all instrumentation to starboard motor. Rpm recover but gauges and vesselview do not. Motor is still running, flawlessly, but i was worried to run with no instrumentation. Stopped, boat, swapped IAC for new and symptoms go away for remainder of trip. Next trip out same story, can correct issue temporarily by shutting down motor but issue persists. Was near end of season so it has been left for winter project

    My though is IAC overheated, and the pigtail shorted the ECM causing my lack of coms only on starboard motor. Motor runs flawlessly.

    This is my thought but if anyone has had any similar issues or other ideas i'm all ears.

    I have searched unsuccessfully for the thread that provided info on a repair of the ECM as opposed to buying new. I believe sferguson had lightning issues and was able to find a race shop somewehre that did it.
  2. juggernaut1

    juggernaut1 Active Member

    Apr 19, 2015
    Perth, Western Australia
    2006 38 Sundancer
    8.1S / ZF 63V Drives
    Whipple superchargers repaired mine......fuel pumps were staying on when ignition switch was activated prior to starting......12 months on, still all good.

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