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Harness compatibility

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  • Harness compatibility

    Hi Everyone. started having problems with my 1986-150 HP Black Max and when i did a compression test to my surprise the top port side cylinder read 85 PSI. Instead of pouring more money into the engine I went and found a 1995 Mercury 115. I got everything set up but the RPM gauge would not work. I measured the voltage going into the gauge and it was at 12V, I measured the sender pole voltage and got a reading as well. I also made sure that the setting behind the gauge was set to 4 (4 cylinders). Could this be a wire harness from engine to vessel compatibility issue?-Thanks, Lou.

  • #2
    Harness compatibility issue. Still haven't resolved this. I checked the wiring and set the pole position to 4 as per online instructions for a motor like this. When cranking the engine the gauge needle jumps up but drops right back. Going to change the lower unit oil and make sure there is not water in there and will be testing the engine with or without the RPM gauge.