battery system in 1996 22' cruiser

[lloyds]

In the 22' I purchased last spring there are two group 24 batteries in the lazarrette. I haven't bothered doing anything with them or even poked around much to see what is happening there, other than monitoring their condition. Thought I would wait till winter to get into it. But, I can see that with my twin 35 hondas, each honda goes to its' own battery and then the switch, when thrown to "both" transmits the total power to the panel in the cabin. Any guesses on if this would actually combine the charging power of both alternators to both batteries when the switch is on "both"? I assume it would. Any idea what would happen if I added a third battery. Was thinking about adding one to power an electric trolling motor for a dinghy.

[Captains Cat]

lloyds, gotta draw a diagram. see where the wires go to everything. Shouldn't be too hard..

Charlie