I just purchased a fume detector to install behind my steering wheel on the dash. I'm assuming that I tie the 12+ V red lead in parallel with another gauge and tie the ground lead to a ground bus? I've never attempted marine wiring before, so I would welcome any advice I can get. Thanks! (By the way, how difficult is it to drill thru fiberglass? )

Drilling through fiberglass is like drilling through wood. no problems at all, just wear some gloves and a mask. Fiberglass itches and you dont need to be breathing that stuff in!!!
As for wireing....yes you can wire the gound to any ground buss you find. they are all common to each other.

As for the 12V+.......You will need to read the directions and see if they say it needs a constant or a switched voltage source. I'm not sure what your installing but if it takes a switched source just use a test light to find one anywhere on the dash. Or you can save yourself some trouble and go straight over next to the ignition switches. you have a constant and a switched 12V sources right there! Good luck

Most dashes are wired jumping the ground and pos. from gauge to gauge (usually for the light in the gauge). If there is an (I) terminal on the gauge it needs a wire swithched by the ignition. Purple is a common color for ignition. The (S) terminal on the gauge is for the sender wire. Good Luck.

Make sure you use a fuse!!!! Other then that fallow the directions and make sure you use a wire that can supply the draw on the unit.

Jon

Racing_Fan.........Also, When you used the holesaw on the drill, two things.

1) Run it slow, otherwise it will heat up the bit fast and melt the fiberglass into the bit causing a clog.
2) When the actual holesaw teeth are about to hit the dash, run it backwards to score the dash. You will have less of a chance to chip the circle.