how can a person install two batteries on a boat?

[navyman]

I was wondering how can a person install two batteries on a glastron cv23, using one and recharging them both any step by step would be great! I have installed a pretty hefty stereo, fishfinder and I may need the spare sometime. Thanks Mike

[victorfb]

installing a battery isolater switch will allow you to keep both batteries charged while only useing one. they can be purchased at most automotive stores. the switch reads which battery has a lesser charge and switches over. common for an RV to have these for charging both the coach battery and engine battery.