The thread on anti-siphon valves remined me that three boats in Puerto
Vallarta had a PYI prop shaft seal slip forward and create a huge leak
in the last year or so. Two of them had extensive damage and nearly
sank at the dock before anyone noticed the problem. The third was
caught quickly.

Apparently the set screws that hold the assembly to the shaft either
worked loose or were not properly installed in the first place.

The solution is to put a hose clamp on the prop shaft just forward of
the seal so it the screws slip, the seal can't move far.

Is anyone aware of other occurances?