I bought a combiner from West Marine for $70, leave the battery switch
at "House" and believe I don't have to switch the thing at all unless I
wear the house bank down too far to start the engine. And then I'm
switching when the engine is off. I turn it to 'off" when I get tied up
to the dock. I always remember to turn it back to "House" because
nothing works until I do.

Capt. Jeff