Abstract: An improved power spinner for rotating a kelly joint having a pipe sub rotatably mounted in a housing with a ring gear on the sub and a motor mounted on the housing for powering the ring gear. A drive gear is connected coaxially to the motor and a shifting arm is pivotally mounted coaxially with the axis of the drive gear. A movable gear is positioned in the plane of the ring gear and mounted on the shifting arm for engagement and disengagement with the ring gear and the movable gear is connected to and driven by the drive gear and rotatable about the drive gear. A control is connected to the shifting arm for laterally moving the movable gear toward and away from the ring gear and for locking the gears together when engaged. The control may include a cam engaging the arm for rotating the arm about the axis of the drive gear with a bell crank connected to the arm and an actuator connected to the bell crank.