I had a diver under the boat today. This boat was in the yard ten weeks
ago. New shafts, props, all new zincs everywhere (tabs, rudders,
shafts, transom, etc.). The diver reports the ZINCS ARE GONE!!! Even
most of the bolts are gone or just hanging. How can this be happening?
If it is another boat, what can I do to find it or to protect against
it without exposing anyone on my boat to AC shock. In the meantime, we
are unplugging from shore power, which is scary, although our bilges
are pretty dry. I read all the posts, but am still confused on whether
it is AC or DC related, and if the isoloation transformer has any
impact. Oh, one more thing. We had a new computerized charger installed
a while back. I wonder if it were wired incorrectly would that cause
the zincs to go like this?

Russell wrote:
Since my post a few days ago, spoke to our marine electrician and the
on-staff electrical expert retained by the Harbor office. We are going
to have to install an isolation transformer in our dock box. This will
cost about $1,000 after parts, labor and some mods to the box. All 90
boats in our harbor that got the notices have to do this, move, or
unplug or disconnect the AC ground from the DC, not a good option.
So, now I see the West Advisor says that apparently solves the marina's
issue with the AC, but unless we separate all the underwater stuff,
like the through hulls, we still are subject to DC corrosion. Can this
be true? What is the real solution to the AC, the DC, the safety and
the corrosion problem? Is there one? We are one of 90 modest boats from
about 28-48 feet, mostly 1970's through 1990's vintage. We all have to
get these transformers now, but the issue is what else do we need to do
once we are on the transformer?