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1994 Mercury 3.0L 225HP V6 No Spark

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  • 1994 Mercury 3.0L 225HP V6 No Spark

    1994 Mercury 225HP, 3.0V6, Carb model. The boat sat for most of the summer unused so I went to add some fuel stabilizer and run it (South Florida winterization) and I now have a no-start condition. I should probably clarify this is a two stroke motor. The oil injection has been removed and I add oil to the fuel when I fill it.

    It's been upgraded to the newer Merc CDMs. The stator is at 1170 ohms for all 6 cylinders (+/- 10 ohms) measured at the CDM connectors. I have the forward harness disconnected at the large cannon connector to rule out the ignition switch or kill switch. All 6 coils are disconnected, connecting them one at a time does nothing. The ECU is disconnected. The shift kill switch is disconnected. There is no continuity on the ground circuit (BLK/YEL wire) to ground. And absolutely no spark on any cylinder.

    My understanding is that even with the ECU disconnected, it should throw a spark at base timing just off the stator.

    My tach reads 200 RPM while cranking (with the ECU plugged in), so I'm ruling out the 12V to the ECU, the ECU itself, and crank sensor as contributors.

    What am I missing? I'm going to throw the batter charger on it. CDM's troubleshooting guide says I should have 250RPM when cranking. It doesn't seem to be cranking any slower than usual; will this really make that much of a difference?

    Thanks in advance for any suggestions. I do have a spare stator and ECU I can throw at it, but I'm not convinced either is giving me a no spark on any cylinder condition.‚Äč

  • #2
    I have the same 3.0L offshore motor, same setup anyway 1994. Its unlikely to be the stator,

    I'd look at the shift interrupt switch, it grounds the black/yellow wire at the coil packs, it temporarily grounds the coils when shifting to pull load off the motor and ease shifting (as I understood it).

    Alternately the neutral safety switch, but sounds like you bypassed that. I'd check the fuses at the motor, theres a couple iirc under that black plastic shroud on the stbd side. I forget what the hell they go to.


    • #3
      I reread your post, it sounds like youv'e covered the bases. I'd agree throw some charge on the batteries see if you aren't under voltage. I'm not so sure on the ecm disconnect thing, I dont have detailed enough knowledge of the setup as (knock on wood) I've never had any issues. The boat mechanics I've talked to say, the ecm rarely causes issues but if does, on this year motor you are boned, they are unobtanium.