RedactedNarrative: V1 is owned and operated by subject who has over 20 years of vessel operational experience and has a Boater Safety Card from Florida since 2009. However, Operator1 purchased V1 the morning of the accident and stated that he did not have any experience operating a vessel of that size (32’ inboard/outboard) or with twin engines. V2 was unoccupied and moored to dock. 
  
  Operator1 was attempting to moor V1 backwards into the slip next to V2. Operator1 stated that while in reverse, he became confused about which engine was engaged. Operator1 realized he was going to collide with V2 and attempted to throttle forward but may have throttled the wrong engine. V1’s starboard-stern (swim platform on the back of the vessel) collided with the port-side hull (one foot above the waterline, about half the length of the vessel) of V2. 
  
  Inspection of V1 revealed all required safety gear was onboard. No injuries reported. My investigation concludes the accident was caused by Operator1s’ inexperience operating V1 and was issued warning for Violation of USCG Navigation Rules.  End of Report.