Andina Marie wrote:
Russell wrote:
We have been eating up zincs, and just had to replace both props. Had
the marina check and they said the power cord gound terminals on our
twin inboard were grounded to the thru hulls. This is in sal****er.
Any ideas on what could be going on, why this is an issue and what to
do to correct it?

For safety reasons, the ABYC specifications call for the shore power
cord to be grounded to the DC ground

OK

which
includes the underwater
metal attached to the engine(s).


I don't think ABYC actually requires this part. It
is often done, but not always.

There is an increasing number of new boats that
are designed with electrically isolated props and
shafts. Without a connection to the shore power
ground, there is little chance for galvanic
currents to be set up with a neighboring boat. In
fact, even through-hulls can be electrically isolated.

It is actually a safe and trouble-free approach,
but it requires an insulating shaft coupler. And,
of course, some special attention to an RF ground,
if there is one. Usually a capacitor with high
reactance at 60 Hz can effectively isolate the
grounding plate.

Chuck

Your cheapest protection is a galvanic isolator. They are on sale for
under $100 at Defender
http://www.defender.com/product.jsp?path=-1|328|303336&id=605562
One isolator can handle a 50 amp shore cord or two 30 amp.


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