[Matta0413]

Have a 2002 31 Open. Went out for a ride the other day and the gauge for my engine battery back was reading 10 volts. Swapped gauges and the problem did not follow the gauge. So the issue is somewhere else. Before I break my butt trying to swap alternators I want to trace the wiring to the gauge. On the back of the gauge there are yellow, blue and one red wire. The red wire is the one that sends the signal to the gauge but when I look at the back of the alternator thee is no red wire so the voltage reading has to be coming from some place else. Is the gauge wired to the voltage regulator? I am thinking I may have a fuse or something that maybe blown as the gauge went from charging to dead in one trip. Thoughts?

[Misdirection]

I believe that on the Tiara with Crusaders, they are setup for one alternator to charge both starting batteries and the other alternator charges the house bank.

So keep that in mind as you troubleshoot.

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[hiccup]

You need to get a voltmeter (even a cheap one on amazon). With that, measure the voltage at the back of the gauge as well as at the batteries. My guess is they do not match.

You can then use the meter to systematically determine where the voltage drop is coming from. With the boat being 20 plus years old there are likely several high resistance contributors but experience tells me that one will be causing the lion's share of the voltage drop.