OK..Just in case, from now on I will make sure all is off when switching.
It's the engine that needs to be off, Alex, not the rest of the stuff on the boat. Even then, again: As long as you have a make-before-break switch that is in proper condition and you don't accidentally hit "OFF," it shouldn't
be a problem. My point is: Why take the chance? Is there some good reason for switching between "1," "BOTH" and "2" while the engine is running? None I can think of.
I tend to start on "BOTH" and then switch to "1" or "2" after the sails are up and the engine's off. That way I don't take the chance of running both batteries down. Then, usually, I just go ahead and start off the battery that's been used when on the way back.