Hobie drive broke twice today

Had an excellent morning keeping Bushy company in the search for the elusive Halibut. Then headed for the SC mile buoy. Almost there and the drive breaks. One turbo fin was hanging by just the pin. The fin's shaft had come out. Did OTW repairs. while worrying that I'd drop a part in the Ocean. The shaft was in pretty tight but I managed to pull it out with my fish pliers. I screwed the shaft snuggly back in. Put the fin on and put the pin back in and secured it with the retaining ring. Fished here and there and drifted back to the harbor. The drive broke again right outside the harbor.
Saw a video in a recent thread where the fins came off, but in it they talked about an Allen retaining screw  that holds the shaft vibrating loose.  My V2 drive doesn't have this. The shaft screws in so the Alen screw is eliminated.
The Shaft seemed pretty tight in both the fitting and in the fin. Somehow the whole foot long shaft must be turning and unscrewing.
I've only done 10 trips on this drive so I'm surprise this is happening so soon.
Who else has had this happen with the screw in fin shaft?  Plumbers tape or Loctite, what's the best solution ?

Blue loctite...

I will second the Loctite. Stuff makes it also impossible to remove them.

Use Blue Loctite, DO NOT USE RED LOCTITE.  I used blue Loctite back in the summer of 09 on my turbo fins for my Pro Angler and they have never loosened up. 

Kurt - My turbo fin upgrade kit came with locktite.  Its a must, owned 4 Hobies upgraded all with turbo fins and never had that problem.

I broke mine again too.  This time it was the turbo fin shaft.  I had to paddle in from 190ft and 5.6 miles from the beach.  It took 2.5 times longer due to a south wind and a swell going the opposite direction.

Yep, mine was the turbo fin shaft. On the 2013 V2 the end of the shaft has about 1/2 " of threading versus the unthreaded shaft and Allen retaining screw in earlier models. After I fixed it the first time - OTW - I didn't do that much more pedaling so I was very surprised that it unscrewed itself in such a short time.

Before you apply blue Loctite, rinse that area well to get rid of any salt deposit and let dry completely. Is there any damage to the threads?