I recommend:
http://www.amazon.com/Boatowners-Mechan ... bc?ie=UTF8[/url]
This book combined with the meter that I recommended should get the boat part of the fishing equation pointed in the correct direction.
Based on my experience I believe that if a boat has a serious electrical problem it can effect other boats. This can happen at the dock where a boat "steals" other boats zinc over the winter. Or on the fishing grounds... sometimes it seems like certain boats will kill the bite. So... get it tuned up!
good luck.
Karl