Lost Zinc

[Analgesic]

I had my boat hauled for the Winter a couple of weeks ago and found the propeller shaft Zinc missing.  This has never happened before and I have no way of knowing how long ago or why it fell off.  I launched in mid May so worst case is that I have had no Zinc in place 5 months.  The boat is in salt water.  I have always heard how important the Zinc is and now am wondering (worrying actually) what might have happened without it in place.  I would appreciate any advice regarding this situation, ie any areas I should look for excessive corrosion or other trouble.  Thanks.
Brian McPhillips

[Ron Hill]

Brain : Don't worry about it as there is no telling when the Zn let go. 
What you have to do on installation of a shaft Zn is this : Hit it with a hammer then rotate and hit it again.  Then tighten the Zn screws and repeat the process a few time to make sure the ZN is on tight.  Also make sure that the Zn you purchase has a BB on the inside for best ZN to shaft contact. 

[Stu Jackson]

Since nobody knows, it's just not worth "going there."  I suggest that you carefully examine the interior components of the "drive train" to see if there is any visual indication of any undue deterioration.  This would include the metals that come into contact with the shaft, icnlduign the stuffing box and couplings.

[Bill Asbury]

Brian, I've owned sailboats in salt water 14 years and had the same thing happen with no apparent problems.  Agree with Ron, just replace the zinc and make sure it's on tight.  Next season you can plan to have a diver clean the bottom occasionally and check to make sure the zinc is still there, and you can also check it yourself when swimming off the boat. 
Cheers!
Bill

[frankr]

Is there room for another Zinc - There should be I have two on my C-36 shaft. I replace one each year. It is usually easy to tell which is the 2 year old one.

[Bill Asbury]

I second the second zinc idea Frank suggested.  Inexpensive and good backup in case one disappears.
Bill

[Ken Juul]

Several years ago I thought about installing 2 zincs.  At the time the boat was hauled at Zanhiser's and I was advised that in the Chesapeake it is really not helpful.  Simply put there was too much zinc available and in the brackish waters of the upper bay the zincs tend to grow a yellow (zinc oxide?) coating that make them ineffective pushing the erosion to the prop.   May be BS, but top of the line marine maint facilities usually don't try to talk owners out of spending money unless there is a good reason.

Any chemists on the board that can shed any light on this?