I wouldn't think a cable would be a cause but the tranny sounds like the cooperate.
If possible try cranking the motor
while in gear
. If it sound hard to turn then I'd be tearing into the tranny.
With it in neutral, try turning the prop shaft by hand. If no go then it could be a number of things causing a restricted rotation.
Check the oil
in the trans too. It should be clear. If milky then water
has ingressed into the oil
More details would help with troubleshooting.