Re: guages going haywire
well if all the guages go crazy but the motor runs OK I wouldn't cut short the trip. You don't need them.
Ground problems are a crazy mystery. Go all the way back to the battery. Just this weekend a friend was having electrical issues (battery would not start motor or let it run although it appeared fully charged). He removed the ground (neg) cable, which was pliers tight and clean. Put it back on and the boat ran fine. Go figure.
Second choice is a low short--not enough to pop a fuse. I had a gas guage (only guage) that would go all squirrelly just before the 20A fuse controlling it popped. Turns out part of the steering wheel mechanism was flexing over and barely touching the power wire to the guage.
get some di-electric grease on your contacts, too.
Often in boats a wire has a rubbed spot somewhere causing these low shorts. A frequent culprit is where a wire lays on top of a structure like the fuel tank under the floor in a tight space. pressure and movement, salt sand and dampness, wear it a little, just enough, and there you go. Also happens where wires cross or where they move (e.g. at the engine). Lots of places that can happen.
To trouble shoot run new temporary wires from source (battery) to device or block, to isolate a short somewhere along the line of the existing wiring.
Good luck. It took me, 2 different shops and 3 different mechanics 18 months to find mine. Meanwhile I went through a bushel of 20A fuses!
