I have a marine power 5.7. I replaced the alternator thinking it was bad as it would charge. With the new alternator (direct from marine power) I've figured out that it won't charge unless I unplug and replug the harness while it's running. It will then stay running until the next time I cycle the engine off then I have to repeat. The voltage sensing wire (purple) always reads correct battery voltage. I've checked the grounds and they're correct. Not sure where to look next honestly.