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?

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

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.

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?


Hello Russell,

I assume this is a relatively recent problem that
isn't correlated with any change(s) in the boat or
its surroundings that you are aware of.

A very common problem is that a nearby boat with a
depleted zinc is obtaining protection from your
zinc via the marina shore power cable (the green
grounding wire, specifically) as the return path.

If so, you can protect your zincs from this
"theft" by installing an isolation transformer or
a galvanic isolator. A third solution is to
isolate your boat's prop and shaft from the shore
power grounding wire. Of course, "pulling the
shore power plug" will solve the problem albeit
while adding a new one. Might be a good precaution
though until the source of the problem is identified.

There are other, less common, problems that could
cause sudden and rapid depletion of zinc (and props).

If you want to pursue it yourself, get a copy of
"The 12 Volt Doctor's Practical Handbook" from
West Marine or BoatUS. It's all in there. Not
really very difficult and there's no danger of
"breaking something".

But if you have more money than time, hire a
marine electrician or corrosion specialist. Get
the book in either case, since it costs a lot less
than a single zinc.

Good luck.

Chuck

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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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Russell wrote:
Thanks all. Here is more info. I called the harbor master's office.
They had a consultant test all the boats in the marina. Over 100 boats
were found to have the same situation as mine and we were all given ten
day notices, to correct, unplug from shorepower or remove the boat from
the marina. The test showed "power cord ground terminal grounded to
through-hulls". I am not sure how they tested, but isn't the same
ground connected to the shafts? And if the AC ground goes to the engine
DC ground post, as ABYC requires, and I assume all our boats comply,
then wouldn't the AC ground by definition then be connected to anything
on the ground strap which is everthing metal on my boat, including the
through hulls. This is all very confusing and seaches on Google bring
up a lot of data, but not a consensus. I would think, to comply with
the marina demand, we would all have to break any connection between
any metal in the water and the AC ground. But to do that, we would have
to remove the AC ground from the engine DC ground, and that is very
dangerous and violates ABYC and every other code. Any ideas?

chuck wrote:

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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Yep - It has already been recommended above:

Install a galvanic isolator

Conceptually, you cut the green wire just as it comes aboard, and insert
the galvanic isolator between the cut ends. Make no other changes
aboard your boat.

If you don't have one, then your zincs are protecting the dock, the
pilings, the electrical conduit, etc, and all the other boats in the marina.

bob
s/v Eolian
Seattle

Russell wrote:
Thanks all. Here is more info. I called the harbor master's office.
They had a consultant test all the boats in the marina. Over 100 boats
were found to have the same situation as mine and we were all given ten
day notices, to correct, unplug from shorepower or remove the boat from
the marina. The test showed "power cord ground terminal grounded to
through-hulls". I am not sure how they tested, but isn't the same
ground connected to the shafts? And if the AC ground goes to the engine
DC ground post, as ABYC requires, and I assume all our boats comply,
then wouldn't the AC ground by definition then be connected to anything
on the ground strap which is everthing metal on my boat, including the
through hulls. This is all very confusing and seaches on Google bring
up a lot of data, but not a consensus. I would think, to comply with
the marina demand, we would all have to break any connection between
any metal in the water and the AC ground. But to do that, we would have
to remove the AC ground from the engine DC ground, and that is very
dangerous and violates ABYC and every other code. Any ideas?

chuck wrote:
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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Hello Russell,

I'm completely baffled!

First, it is nearly impossible and quite a pain to
determine where a power cord ground terminal is
connected to the water unless the boats were
boarded by the consultant. I strongly doubt they
were able to actually establish that claim.

Second, I have no idea why grounding at the
through-hull would trouble the marina or their
consultant. After all, the green wire is grounded
on shore. I suppose they had no suggestions as to
where it "should" be grounded.

Third, taking your posting literally, it appears
the consultant tested the boats, and not the
marina's wiring.

I would think that as a marina customer, you
should be entitled to more of an explanation. For
example, can the marina or the consultant cite any
authority or standard that supports their action.
If there are 100 of you, take up a small
collection and hire your own consultant. You may
even have a legal case. ;-(

To the best of my knowledge, there is no authority
or standard to which boats must adhere in their
wiring. The NEC's jurisdiction is thought to stop
at the dock pedestal. The ABYC standards are
voluntary, although insurance companies may
require compliance with them.

Good luck.

Chuck







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"Russell" wrote in news:1150267403.137578.163050
@p79g2000cwp.googlegroups.com:

Any ideas on what could be going on, why this is an issue and what to
do to correct it?



That's easy. The marina's power system is hooked to ground in a hundred
places, as well as dangling in the seawater under the docks.

There is a complete circuit for your electrolysis hooked to all these
wonderful grounds and underwater conduits because some idiot grounded
your AC power ground to your underwater fittings and outdrive. So, YOUR
zincs, and when they're gone, YOUR OUTDRIVE is protecting the marina's
electrical system from corrosion, like it does to EVERY metal thing it is
hooked to...

Now, where is the issue. First place to look is your battery charger,
the common point to both battery DC systems, the negative terminal of
which is hooked to the engine/outdrive, and the AC power system's ground.
It's supposed to be isolated....Let's test it.

Drag the power cord from the dock post down into the boat so we can get
to the AC ground pin on the dock plug of your boat any ol' place we
want.....

Do you have an ohmmeter and know how to use it?

If yes, measure the resistance from the ground pin on the plug to the
engine block. It SHOULD be open...no connected...infinity resistance.
If it's connected together and shows a low resistance, unplug the battery
charger from the AC power supply, breaking its ground from the AC system,
and measure from the AC ground pin to the engine block, again. If it
opened up, the charger is where they are connected. If it's still
connected, we'll have to start tearing into the power panel to find out
where some idiot interconnected them....probably after reading some of
the posts on this newsgroup where it all gets bonded together to satisfy
some old wives tale that has screwed up many a zinc and prop.

Other places the AC power line can ground the engine block a

**hot water heaters with both AC and engine cooling system heating...
**a jumper wire added to the inside of the power panel from the AC ground
connection to the DC negative bus by some idiot.
**any place else where the systems come together....including seawater-
cooled air conditioners, another electrolysis problem altogether.

The case of the air condition is grounded to the AC line ground....
The case of the air conditioner is also hooked to the seawater by the
seawater passing through its seawater-cooled heat exchanger. There might
as well be a wire hanging over the side and no way of changing it. The
only way I know of to isolate them is feed the AC line through a galvanic
isolator or big isolation transformer like the big yachts use.

Good luck. I can hear your new zincs fizzing away clear over here!

Until you fix it....UNPLUG THE BOAT!

"Andina Marie" wrote in news:1150291413.115563.258890
@g10g2000cwb.googlegroups.com:

For safety reasons, the ABYC specifications call for the shore power
cord to be grounded to the DC ground which includes the underwater
metal attached to the engine(s).


What safety reason is that? The engine doesn't have any AC-powered
equipment, neither do any of the DC-operated equipments. There's no reason
to AC ground anything not hooked to the AC power line.

Have you got a reference to ABYC about this? I'd like to read what it
says, other than "for safety reasons"....

The ABYC requirement is in Section E-11.

Here is one reason:
http://www.bluesea.com/Article_detai..._ID=290&id=299

Here is one result of not doing it: http://www.abycinc.org/lucas_ritz.pdf



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Larry" wrote in message
...
chuck wrote in news:1150314306_2111
@sp6iad.superfeed.net:

I strongly doubt they
were able to actually establish that claim.


Unplug boat.

Measure from ground terminal on boat power cord to marina ground.

Is it open?

Yes, boat ok, no ground problem

No, boat not ok, is causing corrosive electrolysis to everyone else.

A really simple test would be to just hook a test neon light, available at
any hardware store, between AC line hot and boat ground terminal. There's
no reason to connect the AC line ground to the seawater inside the boat.
IF ABYC says yes, it's stupid!

"Glenn Ashmore" wrote in news:l_2kg.112247$Ce1.77235
@dukeread01:

http://www.abycinc.org/lucas_ritz.pdf


I agree with the REAL solution to this problem that would make both the
protection of the boat's underwater metal parts and electrical safety
possible:

"If a Ground Fault Circuit Interrupter (GFCI) breaker had been installed
ahead of the boat’s shore power, 10ma of current would have tripped it
off. The bottom line was that if the boat had been properly wired or a
GFCI placed ahead of the shore power cord, we would have our son today.
This started my asking questions as to why GFCI’s were not required. In
every other place in this country, where you have this deadly combination
of AC and water, it is required. Why is it not in this situation? After
asking around a little, I was told that GFCI’s would never work in this
situation because the moisture content around marinas was too high. But
this did not make much sense to me since GFCI’s are always placed in damp
places such as bathrooms, kitchens, hot tubs, etc. We decided to do some
testing of our own. At this point I decided that I must do something so
that another family does not have to go through what we have and continue
to go through on a daily basis. First, we installed a 30 amp GFCI/Breaker
Thomas & Betts #GFB130 into the breaker box ahead of the shore power cord
of our boat. A $30.00 part. We then duplicated electrically what had
happened the day that Lucas died. The results were clear! The GFCI
tripped in a millisecond, as it would have when the AC problem first
developed on the power boat. We left the GFCI in to see if we would, over
the next few months, develop problems and have nuisance trips. To date we
have had no failures or nuisance trips but we did have a real trip and
the problem was traced to a hot water heater element (see photo). The
GFCI worked"

We simply must make it mandatory by a certain date....or we disconnect
the marina's power and take away their business licenses, giving them the
only incentive a marina ever pays any attention to...the loss of money.

Commercial GFCIs can be set to higher than 7 to 10ma of leakage before a
trip. Humans can withstand 50ma for long times. The current leaking out
of a boat to kill a human swimming in the water is MUCH higher as the
current passing through the swimmer NOT touching hot parts, directly,
quickly spreads through the water. This example, bearing on the "it's
for the children" ploy always used to get human sympathy pumped up, is
very rare. Any boat leaking as badly as this example is very rapidly
going to experience catastrophic failure of all underwater parts from the
intense electrolysis being 120VAC above ground will cause in a few days.
The metal parts underwater will just fizz away rapidly, unless it trips
the marina's cheap breaker from the overload.

Boaters will scream bloody murder for a while as all the GFCIs on the
posts trip when they plug their boats in. That's the price boaters are
going to have to pay because any boat that trips it IS causing AC safety
problems for the kids swimming in the marina.

Immediately, marinas could simply post a sign until the GFCIs are
installed demanding NO SWIMMING IN THE MARINA as you walk aboard their
docks. Of course, as with all the other signs, this would also be
ignored.

Don't you find it amazing how many divers are cleaning the bottoms of
lots of boats and come up still alive and not cursing being shocked?
They all are directly touching all the underwater fittings. I'd think
they would be the first group to demand GFCI installations! They're not.

Typical kneejerk reaction. The rear gate of a 1989 Ford Exploder pops
open and some kid falls out on the street who just happened to be
standing up pushing on the tailgate. Government bureaucrats, and
politicians trying to make the news to get re-elected, overreact and
demand the CPSC recall every Exploder ever produced to force Ford to
spend $23M to replace all Ford Exploder tailgate latches installed since
19XX, causing the price of Fords to increase 4.2 percent next year. If
an adult had fallen out, we'd have said, "Don't lean against the
tailgate, stupid!"

Just knowing how many boaters are secretly ****ing in the water flushing
their heads directly overboard with the Y valve in the let's-not-fill-up-
the-holding-tank position is more than enough to keep me and any kids I
know out of the marina's ****y water....(c;

Yecch!