Re: bow,stern,n dash lights
It's gonna be a process of elimination. Silvertip basically nailed it, however.
Hopefully you have a mult-meter and know how to use it. Start at the battery and do the voltage check as mentioned. Also, if you can run the motor, check to make sure the voltage with the motor running is higher than with the motor off. This should eliminate the charging circuit as a reason for the low voltage.
Also with the motor running are the lights now brighter?
That would let you know there is a battery load or connection problem.
I would go to the fuse block next and see if that same voltage at the battery is present at the fuse block, usually mounted in the console, under dash, or adjacent to the switch panel.
Many of these kinds of problems are due to the environment our boats are in, the water and moisture enhances corrosion and bad connections.
An automotive tester with a lamp on it and a sharp tip can be used to penetrate the jacket of the wire to help eliminate an intermittent open in a wire. Just make sure the ground lead on the tester has a good ground to
connect to. I have added another ten feet of 18 ga. wire to mine to help me move around the boat. Good luck!