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  1. #1
    Member
    Join Date
    May 2016
    Location
    Ellwood City, PA
    Posts
    19

    1996 Mercury 250 EFI head temperature?

    Has anyone checked there head temperature while idling on a hose? I'm trying to figure out if I have a miss on one cylinder or not. Fished a few days ago and it seemed like I'm one cylinder down. Checked compression when warm, 120 to 125 across all cylinders, I have 300 ProMax ECUs and ProMax heads. Injectors cleaned last fall by Brucato, this was before I learned Don does them also. The bottom 2 holes are 130 to 135 degrees and the top 4 are between 145 and 150 degrees. This was taken on the head right beside the plug in the same location of each cylinder. I didn't know if bottom cylinders got the cold water first? I was thinking about pulling plug wires off 1 by 1 to see if there's a sound change, but can't find my insulated plug wire pliers. The plugs looked about all the same color, but I put new ones in anyways.



    1996 Mercury 250 EFI (SERIAL 0G408397)
    Last edited by Tinbanger1979; 06-15-2019 at 05:37 PM.