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1978 Mercury 50HP 2 stroke electric start

C

compton1963

New member
I have a 1978 Monarch Aluminum Bass Boat, The wiring harness that goes from the motor to the remote has dry rotted. I have replaced the harness and was in the middle of changing the ignition switch when I realized on the drawing I have the 7 pin plug. I have a white wire that goes to the igntion switch. However the engine side of the harness has no pin and now where for the white wire to go. The drawings show the same thing. I am stumped on what to do next. I am thinking I am going to have to bypass the plug/ harness in some way and route the white wire elsewhere. But I definitely need some help. PLease advise
 
please see attached diagram. This is as close to what I actually have that I can find. The white wire goes to pin "F" on the ignition and then to one side of the choke. and then yes to the tachometer. But again I do not understand why the pin is missing on the engine harness side . Thanks for your help
 

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  • MERC 500 DIAGRAM.pdf
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I have the 1976 version of your motor and have the same wiring diagram. I think the white is tied to the red in the run and start-run positions and becomes the ignition wire to power the choke switch and the tach. It is not needed on the motor side although I don't know why it runs all the way to the motor harness.
 
After looking through some wiring diagrams for different motors from this era, some of them use the white wire on the motor side. I think the same harness was used on many different motors and not all wires are used on every motor, like ours.
 
ocboat said:
After looking through some wiring diagrams for different motors from this era, some of them use the white wire on the motor side. I think the same harness was used on many different motors and not all wires are used on every motor, like ours.
Click to expand...
Thank You for your help.
 
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