On Tue, 21 Nov 2006 03:38:56 GMT, "Dave" wrote:

If batteries are kept fully charged, is it OK to leave them stored in the
boat (laid up) over the winter? Might get down to the teens once in a
while, but mostly will only dip into low 20s overnight.

Yes, absolutely no problem, just like a car battery.

The key is fully charged or close to it. If you can't run a charger
in the winter time, top them off in the fall and then disconnect the
battery terminals. A good battery will hold its charge. If not, it's
time to replace it anyway.