Help please. I have a 3x that works good except when I am running my outboard motor  (25 hp yamaha 4 stroke). When running the motor it will work a few minutes then go blank on the depth reading or goes very erratic showing very deep readings when I know it's not. I can restart it and it works again for a few seconds then back to bad reading. No issues when outboard is off or idling. 

You don't have the transducer attached to the hull so it can give you depth when the boat is moving faster than idle speed. Post a picture of your transducer installation.