Abstract: A power driven screw jack with manual override for adjusting the inclination of a pivotable backrest in a recliner seat has a housing attachable to the stationary portion of the seat and a screw attachable to the backrest. A nut threaded on the screw is normally fixed to the housing such that the screw may be motor driven to obtain axial displacement of the screw through the housing. A nut release is manually actuatable for freeing the nut from the housing, whereby the inclination of the backrest is adjustable by either turning the motor driven screw with the nut locked to the housing, or by linearly moving screw through the housing together with the nut released from the housing as by pushing on the backrest in case of power failure to the screw motor.