No the bare wire is not a shield, it's simply not insulated. My new monitor showed up today $30 on Amazon, it was delayed a couple of days due to weather, understandable so was I. The wiring on the monitor red, black, and blue. Pretty straight forward red positive, black negative, and blue is for a reverse function. The blue wire gets 12 volts applied to it and it switches to camera 2, I may put this into use later if I hook a second camera to this monitor.
So I got everything slapped together tonight in one of my old DeWalt drill cases, I'm not real impressed with my case setup and will probably redo it. I am thinking about using a 5 gallon bucket for my case and incorporating multiple batteries in the bottom as a power source for lights and flasher also. One thing I did that I believe will be good for me is shorten the camera cord to 30 feet, the deepest water I fish is 20 feet. Most of the time I'm in 10 feet or less. I will keep updates as I refine things.
Actually the other post may have been correct for a different vintage camera. I would guess that Marcum out sourced the cable assemblies so wire colors may vary. When I get time I will get the actual pin out as it would plug into the original monitor.