Hi Meaxculpa
While a faulty neutral switch will cause a "no crank" condition, they don't cause intermittent "totally dead" conditions. From what you wrote this sounds like a complete power loss. Is that right? When you turn the key, no beeps or lights on the control compared to when it is starting cold?
If it is a total loss of power the solution may actually be quite simple even if a bit laborous.
This sounds to me like just a bad connection or possibly a faulty cable. I suggest doing some basic cleaning of all the connections ESPECIALLY the ones for both battery cables. Boats have a MUCH higher incidence of corroded connections than pretty much any other type of conveyance. Electricity NEEDS shiny, bright connections in order to travel. Remember...ground connections are JUST as important as the "hot" voltage connections. As a matter of fact, electrons travel from negative to positive in an electrical CIRCUIT. i capitalized circuit to emphasize this point. It's exactly as it says....the elecrons HAVE to travel in a COMPLETE circuit but many people only focus on the parts of the circuit that have voltage all the time....ignoring the grounds. Don't be "that guy"
Disconnect BOTH battery cables and clean, clean, clean the posts and cable ends. While they are STILL disconnected follow each and find where they connect at the engine. Disconnect them both there and clean, clean, clean the cable ends AND the points of contact the ends make at the engine. See? I told you there would be WORK.
I'm guessing that once you've got that accomplished and hooked back up.....saving the POSITIVE connection at the battery for LAST...and everything there is clean and TIGHT...Your friends issue will have gone away.
But IF NOT....
Since you say you have a METER (hopefully a good quality digital one)
Go online and Google VOLTAGE DROP TESTING. There are many good tutorials and videos on volt drop testing with a multimeter.
Volt drop testing can help you EASILY identify a bad cable, wire or connection AS THE CIRCUIT IS ENERGIZED.
If my little clean up doesn't work you will need to go forward with volt drop tests STARTING with the battery cables.
One other thing that you should use the meter for is to check the CHARGING VOLTAGE at the battery posts. It is possible that, if the battery is being overcharged, the battery could be in "distress" because of it and could also cause this symptom. I doubt it but it's too EASY to check not to check it out. You will want to see about 13.6 to 14.2 volts at the battery while engine is idling and at 2500 rpm. Anything over 14.5 volts is overcharging and anything less than 13.6 volts is probably under charging.
Anyway, I hope this helps you and feel free to ask any and all questions.
Good luck.
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