We have a 1971 Mercury 400 Thunderbolt Ignition outboard motor. Recently we have been having issues with the electrical on the boat. Somehow, even if the boat isn't running, the motor seems to be draining our deep cycle battery. I was wondering if anyone had some insight on this. I'm assuming it has something to do with the wiring because we have ruled out the chance of a faulty battery. We actually bought a brand new battery and it is doing the same thing.