Hi Chrisuk. Have you tried power straight to the motor, but it looks burnt out to me.
John
I would say it definatley is burnt John, A squick sniff inside the hull should confirm it.
If you are confident with an electric Multi-meter/tester, set it for Amps DC, connect it in series with the offending motor and see if it has an amp draw when operated.
Alternatively disconect the motors from their supply (Important to do this, as your tester wont like supply voltage up it, when checking resistance or continuity) set your meter for resistance and just check the resistance across each motor, see if you have a wildly varying reading between motors, or even a closed or open circuit which will confirm the motors up the swannee.
Peter.