I have a 1989 Mercury/Mariner Marathon 135 Serial # 0c125840. I bought an after market tach and never could get it to work. I have all the wires connected in the right spots,(Gray to signal, purple ignition, black is ground. When i turn the key the tach goes to Zero or drops down, like it should. When i start the motor it acts like its going to work and comes up maybe 2 lines and then nothing. I have it set on 6p, I tried moving the brown wire from the switch box today to the yellow wires and nothing. Before trying that it would kick on every now and then but not for long. I dont see the rectifier like they show in some of the pics on this site or in part shops. And my battery volts are 12.6 when its not running and 12.6 when it is running. Any help would be greatly appreciate.
