missing zinc

[David Arnold]

My boat was recently hauled but the zinc (supposedly replaced in the spring by a diver having wintered in the water last year) was gone.  Assuming that the diver did in fact install a zinc is it possible that corrosion could have eaten away at the metal completely?  If not should I assume that perhaps the zinc was not tightened up properly and worked it's way loose?  No visible damage to shaft or prop although the outer edges of the prop could be a bit thinner than might be expected on a boat only 2 seasons old.

[Ron Hill]

David : It's possible, but improbable that a Zn would loosen and not make some strange noises when shifting.  The reason that I say that is both screws would have to back out evenly or both edges of the collar sacrifice exactly the same  - to have it "fall off"!

I had one side loosen/sacrifice (can't remember which) and it made one hell of a racket when shifting.  When I pulled a few weeks later I expected the worst and only found a very loose collar Zn.   It would slide up the shaft and then down banging into the strut!!  Think the diver "supposedly" replaced it this spring.

Don't know about the "thinner outer edges" of your prop.  Electrolysis usually exhibits itself as pitting. 
Hope this helps.

[David Arnold]

Ron, based on your reply I would say I'm pretty lucky as there was no visible damage to the prop, strut or shaft that I can see.  I will be putting on the zinc this year so I will know it has been replaced!  Thanks...

[Bobg]

Just a question, is it really necessary to change Zinc's in Lake Superior?  The previous boat owner said his zinc never seems to corrode.  Also, is there a zinc on the shaft on every 34?  I don't recall seeing one on my boat when I had it hauled, Thanks

[Ted Pounds]

On Lake Michigan my zincs corrode very slowly.  They usually last five years or so, but need to be replaced eventually.

[Footloose]

I would agree that those of us in fresh water get much more mileage out of our zincs than the salt water boats.  I do believe that they are necessary.  Has anyone tried the magnesium anodes?  I haven't been able to find them locally and they are more expensive.  I also haven't seen the need.

[ohana34]

I replace ours every few months here in South Florida and yes I've had them come up missing with no damage anywhere.
Does happen.
Jim