Sounds like a break in the wiring harness. I had a similar problem 3 years ago. A marine mechanic helped narrow down the problem area, and then gave me the option of letting them continue the search (at $60 per hour - or whatever they get), or I could look for it myself. They said to look for a loose wire & sure enough I found it. The original harness had to be spliced when the engine was replaced. One of the connections became corroded & that was the prob.
Good luck,
Steve
Good luck,
Steve