The other day I had my Atomic 4 running while tied in the slip. I had just reconnected the exhaust and was testing a new CO2 detector. I have two batteries on my boat, a new one (no. 1) and an older one (no. 2). The new one I use for cranking the engine. The other day, with the engine running, I moved the battery switch from No. 1 to No. 2, thinking I could add charge to the older battery while there in the slip. Then engine died. I switched back to No. 1 and she fired right back up. I thought that once the engine was running, the alternator provided the current for spark. Following this logic, shouldn't the engine have kept running and simply started charging No. 2 battery? I'd appreciate any insights you can lend.