Re: 1992 Mercury Charging System
Sounds like the dual regulator 40 amp system. It's actually 2 completely independent 20 amp regulators. The rectifiers are built into the regulators. Usually the red wires are tied together at the solenoid, making it a 40 amp system. They can be isolated so one charges the starting battery, and the other charges an auxiliary battery.
The burnt yellow wires connectors are a problem. They're running 20 amps through a 10 amp connector. The heat generated both spoils the bullet connectors and travels down the wire to the regulator and overheats it. I'd cut them out and replace them with a wire nut for testing, solder and heat shrink once things are checked out.
Disconnected, each pair of yellow wires should yield about 15V per 1000 rpm. Each pair will brightly light a 12 volt headlamp at idle, and burn it out in a heartbeat if you rap the throttle. Each pair must be isolated from ground, and the other pair. (ohmmeter testing)
Once you have reliable AC into both regulators, you can disconnect the red output wires from each in turn, and test the other regulator. Look for obvious battery charging, and also connect the tachometer to the regulator under test and see if it works.
Most boats will run on one of the two regulators with no problems.
If you replace a regulator with a used one, stick with one of the black potted ones, or CDI. The clear (yellow) potted ones were not reliable.
hope it helps
john
that's the problem