Find the leak before it takes out the drive.There is no loss of oil unless there`s a leak. fishing line behind the prop for a "rotating leak"?Any gear oil in the bilge? carrier seal or yoke leaking.
Drain your drive & see what the gear lube looks like....
Then pull the drive & look in the bellows for gear lube....
Next, pressure test the drive.......
At least that is what I would do.....JK