Abstract: A coupling mechanism for use in conjunction with a hose reel to automatically and selectively engage or disengage the reel and a motorized drive train. The coupling utilizes a sliding contact element on the drive train which is arranged to automatically engage one of a series of cooperating stop lugs on the reel to transmit the driving power of the motor to the rotatable reel. When the contact element is placed in a first position, it will be disengaged from the stop lug on the reel to allow the reel to rotate freely. When the contact element is shifted radially outwardly to a second position, it will automatically engage a stop lug, causing the reel to rotate under the power of the motor. The radial shifting of the contact element between the two positions can be controlled by stopping the drive train at selected orientations. Also located within the coupling mechanism is a friction element designed to control through a drag force the movement of the reel when it is disengaged from the drive train.