Excuse my lack of knowledge on this topic but I won't know unless I ask. Can you leave your boat in the water(i.e. overnight in the dock) and charge your batteries with an on-board charger? Thanks, Cookie!
Cookie, just make sure the connections are clear of the water or your batteries will get a charge!! Seriously, they are the single most improvement I have been able to come across. Buy quality and you'll not be sorry you spent the bucks.
Cookie, last point about safety: Plug the charger into extension cord at the boat first, then plug the extension cord in at the outlet. In the morning, unplug at the outlet first, then at the boat. NEVER the other way around. Bad things can happen when you accidently step off the dock with a live extension cord in your hand.