Told ya !
If you are really interested in this and any other electric issues I highly recommend you visit Captain David Rifkin's website
and look under "Documents". His website is a goldmine of clear and concise articles on marine electrical issues.
Dave is a retired nuclear sub commander, corrosion consultant to USCG and USN and one of the top guys in this field. I took one of his seminars a few weeks back and was greatly impressed.