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Mercury 115 EFI Missing at all RPMs

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  • Mercury 115 EFI Missing at all RPMs

    I have a 115ELPT4S that has a really bad miss. I replaced spark plugs and seemed to be fine the next time out. The day after that it started missing again. I found that it was missing on the bottom cylinder. I swapped coils #1 and #4 and the miss stayed on the bottom cyldiner. Pulled spark plug and it still looked like brand new (the others were a litte brown) Replaced that bottom spark plug again and ran great the rest of that day and all of the next. Two days later the miss is back and seems to be worse. Tried to bottle feed with gas and just bogged down. The miss is very intermittent, too much so to figure out which cylinder it is missing on now or whether or not it is a certain cylinder this time. Any input would be great, thanks a lot.

  • #2
    Is the motor throwing a code?
    Regards
    Boats.net
    Mercury Outboard Parts
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    • #3
      this is a work boat and the buzzer does not work, the tach does not have any warning lights on it.

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      • #4
        just started it again and it is back to not hitting on the the bottom cylinder

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        • #5
          swapped fuel injectors from top to bottom and still not hitting on bottom cylinder and swapped coils again from top to bottom and still not hitting on bottom cylinder....

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          • #6
            Need to run a compression and cylinder leak down test to see if bottom cylinder is leaking compression.
            Regards
            Boats.net
            Mercury Outboard Parts
            MerCruiser Parts
            Force Outboard Parts
            Mariner Outboard Parts

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            • #7
              Checked and I had no voltage going to bottom fuel injector. Checked continuity and found that there was a break in the wire somewhere. Replaced harness and is running great now.

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