Tamd 61 randomly starts on its own

Recently purchased 1990 Baja with twin tamd 61 diesels. Woke up one morning to hear the port side engine running. This has happened several times since. If the batteries are on the engine will start on it's own randomly. Sometimes days will go by and it won't start and other times it tries to start as soon as the batteries are turned on. I have changed the relays, the harness, and the key switch. The only way to shut it off is to cut the battery power and pull the arm under the stop selinoid. Anyone have any ideas on this one?

Look at the starter, make sure RED (+) cable is not directly touching the small middle terminal or bare wire on the starter (smallest wire coming from the starter solenoid). If they are shorted, it will start the motor.

PS If your key switch ever breaks at the helm, you can start the motor by shorting the + terminal and small terminal on the starter, with a screwdriver or something.