I dont know much about boats so I wouldnt be much help with the batteries you need, but here is a charger I recommend for pretty much anything 6s or under. It also has a built in balancer and charges up to 17 cell nimh/nicad...
I have had great service with these guys and their shipping is extremely fast...
http://www.valuehobby.com/product_de...=13&item_id=87