"The F6 is equipped with a built-in backup battery for the camera’s clock. This charges in approximately 48 hours when 3 V lithium or the optional Multi Power Battery Pack MB-40 (x166) is supplying power to the F6. When the built-in battery is fully charged, it is able to supply the F6’s built-in clock with power for approx. 4 months."
I went out to sea about a week after I posted this thread and just recently got back home. I sent my F6 out and it arrived at Nikon in Melville, NY today so we will have to see what they say about the battery issue, if that is indeed what the problem is.
That's not too bad, price-wise. Overhauling my last F3 ran $210 out the door. The Nikomat that's going in for an overhaul is going to be about $140+tax, so that's pretty reasonable.
Sounds like a plan, re: the F4... I think, once I finish the roll in the F2AS, the F4 will see some use, teamed up with the F2A. Just have to have a couple decent dry days to get out and do some hiking.