I have a stupid question. I have a two battery boat. I have Perko switch Off/ 1 / 2 / All . When I go out I always turn to All. My thinking is both battery's will charge. When at the dock listening to music then I will only turn it to 1 . Should I be doing things differently? Thanks!

no

Yes.

Alternate from "1" to "2" each time you go out.

"Both" is meant for an emergency situation when you need to parallel your battery current if both batteries are below the required starting current necessary.

This is on the assumption that you have two deep cycle batteries and no isolation circuit.

Single engine 2 batteries I've always ran on both. Switch to deep cycle while hanging and starting battery if needed to leave. Back to both to keep them charged.

You probably have to have it in both while running in order to charge both batteries. Is your stereo wired directly to one battery or to the battery switch?

Radio is not wired directly to battery. I think I only need to "charge" battery that I'm using wright?