1976 Mercury 20 hp external wiring harness problem

[mbd20hp]

I have a 1976 Mercury 200 20 hp outboard with electric start (serial # 4354881). I have had problems with the wiring since I bought it (it had been spliced in many places, had taps for fish finders, radios, etc., and had some corrosion), and have a question about the wiring harness. I have cut the wires in the external harness about three feet from the motor, as there were several splices and bad insulation closer to the controls in several places. I find continuity between nearly all the wires in the harness when it is unplugged from the outboard and sitting on my bench. If I put it on a battery, I get 12 volts from the red and black, but a few volts across red and yellow, orange, etc. Same with black across the other wires. The 7 wires look good where I cut them, and the plug looks good. Does this mean something failed inside the plug and the only repair is a new harness? Could it have corroded or melted inside to leak voltage from the hot wire to other wires?

 

[fastjeff]

Probably. New ones are available.

Jeff

 

[timguy]

If you suspect the plug, you can first unhook the battery, then check continuity on each wire while using your multimeter on ohms and carefully pierce each wire on either side of the plug using a small needle, safety pin, or something similar. Afterwards just touch up the pin holes with liquid tape or even paint.