Erratic Temperature Gauge
>"Any suggestions on how I can test the starboard gauge to determine if it is faulty? "
It sounds like you just did. If you fed the signal from the starboard sensor to the port gauge and got a normal reading then it would seem to me that the starboard gauge is faulty. I don't know what kind of gauges your boat is fitted with but most boats, particularly older ones, have pretty inexpensive gauges. If they go south it's generally not worth trying to fix them---- it's much easier to simply replace them.
I have not had the problem you describe with our boat, but I have with a vehicle. If the temperature exceeds a certain amount, as when going up a grade, the temp gauge will sometimes climb to its maximum reading.* A whack on the gauge brings it back down to the proper reading.* In this case (a 1973 Land Rover), the problem is apparently an iffy instrument voltage stabilizer. In the Land Rover, this is a separate little component that's mounted to one of the instruments in the panel. I have no idea if boat instruments use a separate voltage stabilizer for the instruments, if each instrument has its own stabilizer built-in, or if voltage stabilizers are even used at all.
In any case, since none of your other instruments seem to be affected, I would think replacement or your one bad gauge would be your best solution.
-- Edited by Marin at 15:06, 2007-12-26