Jim,
While stationed in the Navy on guard duty I observed a car that had its
head lights left on, it took about two to three hours, if memory still
serves, to extinguish. I leave my radar detector on all the time without
problem, I've come back to the vehicle after 10 hours to find a goose-necked
halogen map light I have left on. Had no problem starting the vehicle.
Paul

"Jim Rojas" wrote in message
...
It depends how much current the radio draws. We all know that leaving your
car dome light on will kill your battery within a couple of hours...

Why not install a Perko dual battery switcher? This will eliminate those
worries about leaving things on too long.

Battery 1 - For engine cranking only
Battery 2 - For Accessories only

Using the perko switch, when the motor is running select ALL. This will
charge & use both batteries for cranking. When the motor is off, select
battery 2. This will only drain the 2nd battery. I use this setup in every
boat I ever owned.

Jim Rojas

wrote in message ...
About how long can a fixed mount VHF radio be left on, receive only,
at anchor, engine off, before the battery is unable to crank the
engine? The radio being the only accessory switched on.

Thanks, HJJ