Battery recommendation

Look through the search feature. Here are a few threads to get you started:

http://www.yachtforums.com/forums/technical-discussion/21986-deep-cycle-house-batteries.html
http://www.yachtforums.com/forums/carver-yacht/21896-best-heavy-duty-batteries.html
http://www.yachtforums.com/forums/t...anence-free-group-31-lead-acid-batteries.html
http://www.yachtforums.com/forums/technical-discussion/12648-replacing-flooded-battery-agm.html

Batteries

D31M work great. Have 6 of them on my boat. My boat is 24v. Two batteries for engines and 4 house. Just recently saw that Sams has a special on the D31for $169.

I put Odyssey dry cells in last year. They work great and are lighter and smaller, in fact I installed two extras that power my 12V Aqualuma underwater lights separately from my house bank. You can fit 6 in place of 4 regular batteries and they are tough, can be placed sideways or even upside down without problems. It is nice having two spares in place in case of a problem far from the dock. If they explode or crack there is no acid to spray around the engine room.

Your setup is factory. Mine is the same way. If things haven't been touched much, very little runs off the batteries on our boats. Simple lighting & electronics. The big power uses (water heater, AC, Refrig) are all 110v. So the separate gen battery ensures you can get the battery charger running if a battery goes dead. Plus you have the parallel switch to start the port engine should it go low from house lighting. If you have an inverter and 12V refrig now, then this setup is not the best.

A few of my friends in both power and sail boats changed to Gel. Ended up back to lead acid. Don't forget your battery charger can only charge one type of battery (if it is new enough to switch between kinds) so you need to change the new gen battery to match any change to the 8D's.

I'm leaving well enough alone with the lead acids.

My 8D Lead acids blew up twice in the last 5 years, no one seems to know why. They must have sulfated and when I hit the starter they arced and blew up. Quite a mess, got me in the habit of carrying several big boxes of baking soda on board. One time we were in the far Bahamas and I had to use jumper cables (Also keep those on board) to start the main engine that had the blown battery.

I changed both alternators and the battery charger the first time and then it blew again a year later. This was the original reason I changed to dry cells, but I like them, they are lighter and smaller, but of course cost more. The first time it blew I was in the engine room using a bump switch and was luckily in the front near the generator and didn't get splashed with acid. I did have a hard time breathing as I ran out the back past the batteries.

I have been using this for many years: Marine: 5000 SP Series Battery Chargers 30 amp No issues and many positive reviews on web forums.

My boat is in storage at the moment, but I think I bought Odyssey PC 2250's. No issues and very happy so far. You may have to do a little work to your battery box as two 2250's are not as long. I solved this by installing three on each side, two used for underwater lights with their own charger, also gives me onboard spares in case of a battery failure. I also seem to remember that the Odyssey owners manual said to leave the Charles Industries Battery charger I have set to wet cell for better performance.