Unlikely it dissolved off due to electrolysis.
Most likely you did not put it on correctly?
Put another on and dive on it once a week.
Brass prop shaft - I have never seen one - only SS.

stu



"Rob" wrote in message
om...
I have a Catalina 30 with an inboard diesel that I launched in May of
this yr- this weekend while swimming off the back of the boat I took a
swim below with a mask to check out the bottom. I noticed the zinc I
just put on the brass prop shaft 3 months ago was missing. I put it
on myself and remember how tight I made the screws- is it possible for
it to either fall off from vibration or deteriorate that fast? The
rudder zinc is still there. I keep my boat at a private dock in a
creek- the closest boat to mine is about 100 yards away. I have shore
power- is the AC ground possibly doing something to speed up the
galvanic process? Any ideas on how to replace the zinc without
shelling out for a short haul?

Thanks-
Rob