My boat doesn't have a breaker between the 30 amp shore power inlet and the main ac panel 2 feet away. I removed a charger/inverter that had been wired directly inline from the output of the shore power/generator switch to the main panel with no breaker or means of taking the inverter off-line. Of course it was wired with solid copper household wire.
When it failed, I had no ac power until I bypassed it.
I would like to install a ELCI breaker in the circuit. Should it go right after the shore cord inlet, or after the shore/generator switch. Keep in mind that I may want to install a charger/inverter at some future time. If so, it will be wired between the shore/generator selector and the ac main panel. I will also install a switch to bypass the inverter in case of failure. Hope this makes sense.