What happens if you run an outboard with an alternator and your battery switch is in the off position? Does this blow the diodes?. This would be assuming you use a manual start. Anyone actually know? Ernie
Also thanks to all who answered my inquiry on opening ports on my O'Day 25. They were Beckson and the new gaskets and screens are in and all leaks have ceased. A real improvement.
If the battery switch is in the Off position, it's like taking the two conductors from your outboard's charging system out of the circuit, separating them, and running the engine, which is perfectly acceptable. I've done this many times myself. As long as you don't put the two wires together, it's OK. My Johnson Outboard came with a couple of insulating covers over the ends of those wires so that you could use the outboard without connecting it to a battery. One wire is a positive which goes to your battery switch. The other wire goes to the negative terminals of your two batteries.
The battery switch gives you a choice of which battery you want to charge with that positive wire from the engine charging system, and when the switch is in the Off position, it merely opens the circuit so that neither battery gets charged. It's very similar to removing the wire from the switch. At no time do those two wires come together and everything is cool.