Re: Johnson 40 Electric Seahorse
What are you going to be using it for? If just for starting, and a few accessories like running lights? If that's all, just go to Wal Mart or elsewhere and get a plain ol' group 24 car battery. Avoid the cheapest one, but you don't need the most expensive either.
EDIT: "Group" refers to the physical size demensions. Has nothing to do with quality, warranty, or anything else. You don't necessarily have to get a group 24, that's just the most popular size, and fits most battery boxes.