I talked about this before, but could not fine it in the archives.

You can make a EMI (electrical interference) detector. Take a small am/fm radio (I have used an old walkman with head set) and tune it AM lower band between stations. Tape a metal wire to the back of radio (coat hanger will work). Use the wire end to follow wiring about boat. The noise, if any will get louder as you approach the EMI source.

If you got a friend in the cell phone business, he/she may have a cell meter. It will do the trick too in most cases.

Some of you old radio guys probably remember this.

I use an EMI sniffer probe on my O'scope when, and after I can't guess my way thru the problems. Pain in the butt to do this.

It is cold here.