Car Batteries

I've got an electric party boat that runs on four car batteries and they need to be replaced.

I just went on Walmart's website, checked several batteries, and none appeared to have the amp hours listed.

Is there an easy button (i.e. Costco's Belchfire 2000 series for the win) or is this a shop around to see who has the best deal this week kind of thing.

I'll post the specs. for what's currently in the boat tomorrow...for now I'm just asking about company and product line.

BTW, they'll only see ~30 hours of operation per year and will live in mild Southern California weather but will get fairly deep cycled, say 50% drained, about 10 times per year.

Thank you in advance for any guidance. 

For an application like that,I would look into lithium or AGM batteries. Batteries plus usually has good prices on agms, but I don't know offhand who makes good 12v lithium batteries. The lithiums I've dealt with were all homebrew.

Check rock auto, they have some surprisingly good prices on batteries.  I think i got that tip here.... My datsun now has a Deka AGM

Find a local battery recycler that does refurbishing they'll likely have some options that'll double your available output.