A watercraft lift with hydraulically actuated arms which self-installs a fitted three-dimensional watercraft cover on a powerboat. A mechanism enables a linear actuator to drive a swing arm up to 180 degrees. The upper end of a two part arm articulates mechanically as the arm moves to reduce vertical elevation while operating. A spring-tensioned elongated roller keeps the cover tight and self-rolls the cover on the elongated roller when the actuated arms are pivoted forward. The mechanism can be attached to the guides of most watercraft lifts.