50hp Mercury ignition issues

[Casey Marionneaux]

I have a 80's model 50hp Mercury I just mounted on a pontoon boat. Runs great but when I mount or make contact with the controller to the hand rail, it kills the motor. There's definitely stator power coming through the controller housing because it will sting me a little if I touch it with the motor running. I changed the key switch because the key was lost. I checked switch wiring over and over and it is correct. This was an issue before the switch was changed also. According to the drawings, the place that shorts the stator is the key switch and the tilt mercury switch. What's confusing is that the motor is mounted to and aluminum transom which is part of the hand rail where the controller is being mounted. It seems the stator power is coming through the shift and throttle cables.
Any ideas?
Thanks

 

[MikeMan]

You could try undoing the killwire that connects when the key is in the off position and seeing if that fixes the problem of engine stopping when its touched to rail. Im picking that the wire that links back to the stator has shorted to the control unit somewhere. It could also be the wire to the tilt switch too so try disconnecting that
Dont totally discount a switch manufacturing error too