RedactedNarrative: New boat owner unloaded boat off of trailer into river before starting the motor.  Boat started drifting down stream and would not start. Boat started taking on water in the aft of the boat.  Boat owner did not know about puting the plug into the back of the boat.  Boat would not start and sank about 300 feet down stream of the boat ramp at approximately 40 feet off of shoreline.