Prop shaft couplign set screw broken

[phorvati]

So I had a broken prop shaft coupling set screw when i first bought the boat. See pic below.

Since then, I drilled it out, ensuring threads are not altered, and put two new set screws along with some permatex anti seize compound and seizing wire across the two nuts. I am fairly certain set screws are aligned with the shaft dimple. When i was installing the set screws last year i made sure to feel for the dimple in the prop shaft while hand tightening the set screws. Then finishing them off with a wrench and sizing wire.


I am at about 20 hours into the engine, and a year later and i am noticing that screws are loose and sizing wire is the only thing preventing them from coming out.
I havent taken a good look at them yet but i have a feeling the screws are broken again. Shaft alignment looks very good with engine in gear. I do have a transmission leak which comes out of the coupling, basically sprays transmission fluid while in gear. (borg warner 72C series). So i am not sure if one is related to the other.

There is no room for me to separate the coupling while in water. So i am wondering until next haul out, what can i do to make sure set screws are in and dont back out. If they are indeed broken, i am thinking of putting new screws and use them as a backing screw with maybe locktite instead of anti seize and put new seizing wire.
I am reluctant to drill through the shaft, that would be some job. But i do need to motor likely 10-15 hours over the 4th of july Holiday.

Any other ideas?


At next haul out i need to replace the transmission and i will likely need a new propeller shaft as i am getting rid of the ancient walter down angle drive.

[phorvati]

I took a look last night, and the new screws were just loose. I put red locktite and re-tighten and then added seizing wire. While they were out, I was able to shine a light in the hole and it looks like they are perfectly aligned with the shaft dimple.

I am just going to keep en eye on them.