I connected the hour meter to the power wire for the engine panel lights and it comes on when power switch is pressed and the engine/tach isn't running. I don't think that's directly connected to the alternator electrically, but then again I don't understand the internal wiring for the tach.

Still not sure if this is the issue but it's certainly a likely suspect. This hour meter will be re-wired before I power on the engine again, that's for sure.