One other thing, why was there enough resistance to cause the key to pull out of the keyway on the shaft to begin with. There could be growth on the prop that is preventing it from turning, line wrapped around the shaft, or could be a bad cutlass bearing. If you disconnect the coupling, can you turn the shaft at all? That may be the cause and if not addressed will happen again once the flange is replaced. Remember to fix the cause not just the symptom.