Abstract: A drive unit for a ski tow rope. The unit has a main frame with an engine having an output shaft mounted in the main frame. A drive pulley is driven by the output shaft and has a circumferential channel to receive the rope. Guide pulleys direct the rope into the main frame, around the drive pulley and out of the frame. The guide pulleys are made up of a pulley at the leading edge of the frame to receive the rope, a pulley at the trailing edge of the frame and a pair of holding pulleys adjacent the drive pulley and positioned to ensure that the rope contacts the maximum possible amount of the circumference of the drive pulley. The holding pulleys are able to pivot.