Normally the parallel switch combines the 2 engine batteries. It's not connected to the house battery. Usually the house battery is isolated except for charging. I say normally because you never know what a previous owner has modified.
I has a similar issue once except my house battery was bad. I didn't really know at the dock because the charger was keeping everything 12 volts working. I had the blower on and once I turned the charger off it just about completely stopped. So I kept the charger on with the blower, then right before I was ready to start the engines, I turned the charger off. Once the engines started they charged the house battery and the blower came back to life. Not sure what you do if you are on the hook. I guess you keep the hatches open as long as possible and hope for the best. You can't start the genny.
_________________ --2002 3880 Regal Flybridge | Twin Merc 8.1HO **Seven** --2003 AB 13 VST Console Inflatable | Tohatsu 40hp TLDI **Phish'n ski** --310 Mercury Inflatable | 1982 9.9 Johnson
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