[sluggo]

You'll lose memory settings on your stereo! Also co detectors won't work so if your in a tightly sealed barn that's heated by a furnace with a cracked heat exchanger it could be bad. Lol .

sorry to jump in here, but how would that be bad no CO detectors?  The only way I can think of  is, if he were spending the night or sleeping on the boat.  If he is not on the boat, and its in a garage, I dont think there is any problem storing it without batteries.   Maybe I miss read something.