Upd.ate. I am always disappointed when someone bring a question to a forum and never reveals the ultimate resolution. I have heard from Grady White and am well pleased with their reply...
"Begin quote:
Dan,
When you start the engine, the cranking cable coming off the battery switch sends power to turn over the engine from the selected battery (usually Stbd 1). While the engine is running, the engine alternator sends power back to the starting battery (Stbd bank 1) thru that same cranking lead. Since the battery switch is in the recommended Batt 1 (STBD) position, Batt 2 (PORT) is not getting any power fed to it.
The Engine Isolator is connected to the engine thru the rigging tube (behind the livewell on your boat), and allows the engine’s alternator to divert part of its power output to Batt 2, to help maintain its level of charge, while still sending the majority of it’s current to Batt 1. That way if Batt 1 ever were to fail, Batt 2 will always be in ready standby to provide power to get you back into port. This is also why we don’t recommend using the BOTH position of the battery switch, except in emergencies, as it can eliminate having a backup battery.
So keeping this breaker on is important, except when performing maintenance on the engine. Hope this helps clarify the situation. Let us know if you need anything else!
Sincerely,
Cameron Merrow
CPO, USN-Ret
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I have not been able to check this out on the boat yet, but am confident it will be as Chief Merrow has described. I have also suggested that Grady may want to update the documentation for this boat and, I assume others.