Hey, Rob--

Prop shaft zincs are easy to install--incorrectly. I suspect yours has
fallen off, not withered away from electrolysis, not in just three months.
And I don't think you can install one properly underwater. Here's why: the
vibration from the engine turning the shaft loosens the setscrews, and
eventually the zinc flies off. I've had this happen repeatedly, until I hit
on my current technique. With the boat out of the water, screw down the
zinc as tightly as you can on the shaft, and be sure to use some LocTite on
the threads. Now begin tapping it with a hammer, and retightening the
screws as the zinc fits more and perfectly around the shaft. Eventually you
will not be able to take up any more on the screws, but you'll be surprised
at how much slack you've created by the hammer-tapping. Unless you have
truly big league biceps, you won't be able to tap with sufficient vigor
underwater. I suppose you can try it, but if so, check frequently to see
you haven't lost the zinc to vibration.

Cheers and fair winds,

Dick Behan
Westsail 32 CAPER
San Juan Islands, Washington


"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