Simply put: how long does it take before your system dies after you turn the boat off, park, switch it over to one battery (of the two, three..?), and blast music?
And what kind of batteries are you running?
For me, it's about 30 minutes, and I'm running two Optima blue-tops. What happens first is my music will keep playing, but the sub will stop. That's how I know it's time to switch to both then run the engine. Does this sound normal? Any suggestions on keeping my stereo running longer? I'm running JUST interior speakers (aftermarket), aftermarket deck, 10" sub, 3 amps, 2 Optima blue-top batteries.