See,
All of those problems can be bad ground issues. Get a 12v test light and go to the thing that have problems and check that the test light has a good ground and then test the power connections to what ever. If there is power there, then look for power on the ground side. If there is, then follow the ground wire down to the rusty connection to the frame.
Before the depression I had a business that was supposed to be doing boat work. But when clients found out that I could find and fix things like this, I had lots of work before the money ran out.
Matt