Was riding and all the sudden the motor would rev with the throttle, although no propulsion, and just an ugly whirling sound of sorts. I can move the motor flange coupling by hand, and everything inside the hull spins fine. I can hold the impeller shaft still while the motor flange moves, and visa versa. I assume there is some coupling connecting the impeller shaft to the motor flange that is messed up. Although, I cannot seem to decipher what it is from the Superjet 2004 diagrams (see below). Any suggestions where to start?