shifting problem

Any suggestions on where to start looking for the problem? I hit something while running wide open and now I cannot shift the motor into reverse and the motor makes a clanking noise while in neutral. The motor will shift into forward and run. After I trailered my boat I spun the prop and it roatated but made a clanking sound on each rotation. This is a 25hp yamaha four stroke outboard. Any suggestions would be appreciated.

[boats.net]

Remove the bottom drain screw in lower unit to see there is metal in lower unit oil, if metal there then it has damage inside lower unit.