Re: Answer for the question "Can I just use a automotive electrical part?"
Alright, I used to be a firefighter for about 6 years. There is almost no way to determine the cause of, especially, a boat fire; there are just too many variables involved in the equation. Unless the source of ignition is blatantly obvious, the fire marshal will determine an inconclusive cause. It could have been something as simple as a fuel leak form one of the boats, and some idiot on the dock threw his lit cigarette butt into the fuel floating on the surface of the water - and there you have it - a live fire traveling rite up the path to that fuel leak. Of course, this is only speculation. Boat fires are extremely dangerous due to the short length of time it takes for the fire to spread from one boat to the next - fiberglass goes up like paper and the new plastic fuel tanks melt like butter. About 15 years ago one of the boat storage yards here went up into flames and it was utter bedlam.
As previously mentioned, this is only speculation. I cannot remember how many times at fire scenes I could hear some idiot bystanders looking on and blabbing: "yeah the fire started because..."
My point is this - DON'T BE THAT GUY.