RedactedNarrative: Vessel 1 was conducting training at the docks at Brewerton Boat Yard specifically working on docking. Vessel 2 was tied up on river side of dock and was unoccupied at time of accident. V1 was parallel to V2 and attempting to dock in front of V2. Operator of V1 placed vessel in reverse to maneuver stern of V1 closer to dock and in doing so inadvertently hit his arm against the port throttle in revers causing V1 to strike V2. Specifically the steel engine guard/ cage on V1 rubbed against the port bow of V2 causing two approx. 8" scratches in the fiberglass.