1977 mercury 500 external wiring harness

[JRM80]

I acquired a 1977 merc 500 a while back and am just getting around to looking at it. It refused to start and wouldn't even pop. I found that there was no spark at all and I've identified the problem as the wrong cable from the remote control to the engine. My engine has a 6 pin male socket on the side of the motor but the cable and remote control box that came with it has a 7 pin female plug. The plug fits into the socket on the engine ok, but the additional pin on the plug is the one that carries current to the ignition system. Since there is no pin on the engine socket to engage the corresponding socket on the female plug, no current is flowing to the ignition system. Clearly the remote control box and external wiring harness that came with the engine are the wrong ones for this engine.

I have yet to hear this engine run and would like to patch it together enough to get it running and decide if it is worth spending the money to get the correct wiring harness. My question is: Can I run a separate wire from the battery to the ignition circut, and if so, where would be the appropriate point to attach the wire to energize the ignition circut. The choke and starter function properly from the control box, so everything seems to be ok except the ignition circut. I just don't want to fry something further down the line by running the extra wire to energize the ignition system.

Any help in this regard would be appreciated.

Jim mccarthy

[boats.net]

The red wire in remote control harness is the 12 volt positive wire to ignition switch. The purple wire from ignition switch is the key on power wire.