RE: Headliner Panel Removal
"How did you run the radar cable? I assume once you pulled the panels, the existing wiring from the mast was clearly visible. Where did it go from there? Is there a channel down to the engine room from where the cables ran forward to the base of the channel that runs up along the left side of the door along the lower helm?"
Yes the existing cable wiring from the mast was clearly visible. The old cabling did not run into the engine room but ran from the base of the mast forward under the headliner to the instrument "cabinet" overhead of the lower helm, then up to through a hole to the flybridge under the dash. (The old setup had radar only on the bridge). I removed the old radar cabling/wiring starting from the radome end. I connected a long, strong cord to that end of the cabling so that as I pulled the old cabling out, the cord followed it. After the old cabling was removed, I attached the new cabling* to the end of the cord up on at the radome end of the mast and by pulling the cord from below, I gradually worked the new cabling down the mast, then horizontally through the overhead from which the panels had been removed, to the instrument "cabinet", thence up to under the flybridge dash. My new Garmin MFDs and radar are N2K and the radar cabling plugged into the N2K backbone that I installed under the flybridge dash.
From the backbone, the GPS and radar wiring to the lower helm MFD would not fit through the small plastic pipe/hole under the flybridge, that leads into the wiring channel that runs down by the helm door, as it was stuffed with many other wires. So I had to run these wires down through a new hole I made into the instrument "cabinet", then out the stbd side of that cabinet with a new hole, then along the outboard side of the window valence, then through a new hole into the side of the top of the wiring channel by the door. From there I was just able to stuff the wires into the channel and run them down it to under the lower helm dash. I think that I did have to drill a new hole uner the dash to lead the wires through.
Also, I did have to cut the N2K (ethernet?) plugs off to run these wires. The instructions said not to do this but the company that I bought the Garmin stuff from said go for it and gave me clear soldering instructions to reattach them.
The radar cable plug also was a frig to feed at points and I had to enlarge a hold or two.