RedactedNarrative: Vessel entered Marine to park the pontoon, and did not get close enough to the dock.  Operator backed the vessel up to attempt to bring it forward again to park next to the dock.  After backing up, the Operator steered it forward, and the back end of the pontoon turned clockwise and bumped something.  Operator thought he had bumped another pontoon's metal float tube.  Operator heard something bump, but did not feel anything.  Operator successfully parked the pontoon and inspected the motor of the rented pontoon.  Operator looked to see if there was damage to any other boats, and did not notice any damage.  The boat he would have bumped was stationary, and there was no one operating it.  Vessel 2 motor damaged.  The fin on the bottom of the motor was bent and the end was broken off.