RedactedNarrative: Operator advised me that he and his wife had just left the dock, and were heading out for the day. Operator backed the boat out of the marina slip, and placed the vessel throttle into gear in a forward direction. He advised me that he accidentally pushed the throttle too far forward, subsequently losing control of the vessel and colliding into the stern of a vessel docked a couple of slips down. The bow of the vessel collided into the docked vessels port stern, causing damage to the motor cowling and power pole. The struck vessel also received scratches to the gelcoat and rub rail on the starboard side, after drifting into a piling.  The vessel operated by operator did not have any visible/significant damage