i have three deep cycle batteries on my 2001 vyper with two switches, the boat has sat the last two years before I bought it and all the batteries need to be replaced,first of all why are there two switches that show 1-2-and both on the selector? Second when ther shore power is plugged in are all of the batteries getting charged? What batteries would be the best for my application? Was there ever an owners manual printed for this boat? thanks for all of your help.

when the charger is powered all batteries are being charged. You will have to determine which battery is the house battery and which batteries are the engine batteries. Buy one deep cycle for the house and two cranking batteries for the engines. If you have two on the starboard then most likely one of those is the house which will power that bus through the port switch.