So, I almost sank my boat yesterday. I was doing some work on my engine and wanted to test it out. While still tied to the dock, I put it in forward and then reverse. As I was throttling up in reverse all of a sudden the RPMs spiked. I thought I had done something to the transmission but then my bilge pump came on. I looked down below and sure enough, I had a 1" stream of water shooting into my boat. The prop shaft had shot out the back. I had the leak plugged within a minute so no harm was done. I don't know if the set screw backed out or if the set screw wasn't properly in the dimple. Anyway, I have the shaft back in, the set screw is in the dimple and wired to the other one. Even though it is set up properly I am still paranoid. I know that some boats have a safety collar to prevent the shaft from coming out but this boat doesn't have one. What have other people done? I am wondering about drilling a small hole in the shaft and putting a pin or bolt through it. Something that would be set up so it could pull free from the engine but be stopped at the packing nut. My motor only puts out about 15-20 HP so the shaft is way overkill and I don't think a small hole would compromise the integrity enough to be a concern. Thoughts?