Battery switch confusion... advice

[jg91604]

I am confused about the battery switches on my Beneteau 323.

Three switches: house-engine-neg..
info: batteries- 2 group27 house & 1 group27 engine
alternator: 20amp
charger: 20amp
equipt.: GPS,utopilot + plus wind, tridata,lights...

Here is my question... I can start my engine with either or both batteries switched on. When I am sailing, I turn OFF the engine battery, but does that really isolate that battery? Also, if I am running the engine to charge my batteries, does having one off give more charge to trhe other bank?
thanks

[skyellab]

When I am sailing and from time to time running my engine to at least leave the dock or come in I have everything on. When I am at anchor or dockside I turn the engine battery off so it is available when I need the power and it is not drained. Your battery charging system should be wired to charge even if the switch is on or off. The negative switch will take it out of the loop as the negative is gone and it is not a battery anymore.