If the batteries listed above give you sticker shock, you can also look at wet cell batteries. I really like DEKA DC31 in the marine master line. That is if you have room for a 31 series. I used to use the AC Delco batteries and interstate bought them out. I noticed they copied Delcos maintenance free design in the 31MHD battery I got for starting, so if their marine batteries are the same (no water fill caps) I would try those since you have a connection. Both of these batteries should be in the $105-115 range and I got 4-5yrs service as long as I maintain water levels.