Here's a link that should answer many of your questions. Here's another link with a lot of good info. Battery group really only refers to dimensions, important for automotive applications, but not so much on marine stuff. Deka also had a marine applications link where you just look up the cranking amps for brand, and size of motor, but can't find it today for some reason. I think the requirements for a carb'd V-6 are generally about 800 CCA, but I'm sure you can get by with less. Separate starting and deep cycle batteries with a selector switch and/or and ACR is the optimum setup.

So can you mix batteries if an ACR is installed or will the charging system fail trying to charge a starting battery and a deep cycle battery as No Bones stated in an earlier post?

Maybe Ken knows something I don't, as he's an electrical engineer and I'm mechanical, but I don't know of any reason the alternator would actually fail if it had relatively low output compared to battery capacity. More likely you'll just end up with an undercharged battery IF you have a large deep cycle battery and you pull a lot of amps out of it running accessories and either run time and/or alternator output is too low to replace the amps used.

This may be why a lot of bass boat guys who run big live wells AND trolling motors also have permanently installed 110V battery chargers on their boats. I think it's basically just a conservation of energy deal. You could have a huge battery and a little dinky alternator, but if accessory loads were small, you'd never have a problem. The alternator on my old 1975 115 only put out 6 amps, max! (With NO voltage regulator! If battery was fully charged, it just boiled water!) My only accessories were the VHF, running lights and a depth sounder. (This was BEFORE GPS existed!) Yet I ran both starting and dual purpose (think HD starting or light duty deep cycle) batteries with a selector switch for 31 years and never had a problem with that dinky little alternator!

sears AMG
no issues for 3 years now

Been a long time since you have been on the forum, good to see you are still kicking!! :)

yeah, still lurking. LOL
Boat is still in Apollo doing well. How about you?