I lost a zinc on my prop shaft very quickly. My boat is moored with only
one other boat within miles. The only possible source on my boat (I
think) is the bilge switch in my bilge because it is the only thing on.
The connection to the switch is out of the bilge water, so it can only
be coming from the switch itself. I have a voltmeter. Is there any easy
way to test to see if the switch is leaking current?

Stephen Trapani wrote in news:Fyt1o.18052
:

I lost a zinc on my prop shaft very quickly. My boat is moored with
only
one other boat within miles. The only possible source on my boat (I
think) is the bilge switch in my bilge because it is the only thing
on.
The connection to the switch is out of the bilge water, so it can only
be coming from the switch itself. I have a voltmeter. Is there any
easy
way to test to see if the switch is leaking current?


The negative terminal of the battery and battery charger are hooked to
the engine block.....and the zinc on the shaft, probably......

Drag the dock cord dock end into the boat with the cord plugged into the
boat and measure resistance between the ground pin on the dock plug and
the engine block. I, personally, think there should be NO connection
between the dock ground pin and the engine block through the battery
charger. That will start an interminable argument about safety, but I'm
willing to stick my neck out in the name of zinc survival. The battery
charger's DC circuit shouldn't be connected to dock ground because that
will form a huge battery because the dock ground is GROUNDED! You now
have a shorted battery formed between the bottom of the ocean the dock
ground is connected to and the prop shaft with the ocean as
electrolyte....eating the zinc. If the engine block is NOT connected to
the dock ground pin, current cannot flow through it eating the zinc.
The only current, then, would be the battery formed by the shaft/prop
steel/brass/potmetal and the zinc, a much, much smaller battery current
eating the zinc.

The other important test uses the ammeter of the digital voltmeter or
analog VOM. Leave the dock cord unplugged from the dock, but plugged
into the boat. plug one lead from the DC ammeter into the dock socket
GROUND socket. If you're not absolutly sure which that is...DO NOT DO
THIS TEST. TOUCHING THE HOT AC POWER MAY CAUSE PERSONAL INJURY. Turn
off the dock breakers before doing this test, anyways, as it doesn't
unconnect ground.

Now, with the DC milliameter connected to the dock ground, touch the
other lead to the boat ground. The current should be ZERO DC CURRENT.
If you see a measurable DC current flowing to/from the dock ground,
there's your zinc problem....the zinc is protecting the entire
electrical system of the local power company all the way back to the
generator house! This is NOT good.....

Sometimes the ONLY cure is an isolation transformer that completely DC
isolates the boat from the dock electrical system, the best solution for
cruisers going overseas. The little diode isolators work ONLY if there
is no leaking AC power in the system. If you've ever looked under a
marina dock, you know the chance of that is damned near Zero. Those
half-eaten conduits drooping into the seawater, flooded to the core,
will never get fixed unless it blows the main breakers or makes a dock
transformer explode in the night.





--
iPhone 4 is to cellular technology what the Titanic is to cruise ships.

Larry

On 7/20/2010 10:10 PM, Stephen Trapani wrote:
I lost a zinc on my prop shaft very quickly. My boat is moored with only
one other boat within miles. The only possible source on my boat (I
think) is the bilge switch in my bilge because it is the only thing on.
The connection to the switch is out of the bilge water, so it can only
be coming from the switch itself. I have a voltmeter. Is there any easy
way to test to see if the switch is leaking current?

Here's a quicky check: with no connection to shore power at all, find a
meter with a sensitive current scale like 50 microamps. Find a lighting
cord and connect the two wires at one end to the battery terminals. At
the bilge, connect one battery lead to the meter and dangle the other
meter lead in the water, preferably though a scrap of stainless sheet.
Check the reading.
Now connect the meter lead to the OTHER battery lead and dangle the
other meter lead in the bilge again. If you normally leave the boat
connected to shore power, repeat these two steps with shore power
reconnected.

Not a complete check, but it can catch many leaks.

Brian W

Larry wrote:
Stephen Trapani wrote in news:Fyt1o.18052
:

I lost a zinc on my prop shaft very quickly. My boat is moored with
only
one other boat within miles. The only possible source on my boat (I
think) is the bilge switch in my bilge because it is the only thing
on.
The connection to the switch is out of the bilge water, so it can only
be coming from the switch itself. I have a voltmeter. Is there any
easy
way to test to see if the switch is leaking current?


The negative terminal of the battery and battery charger are hooked to
the engine block.....and the zinc on the shaft, probably......

Drag the dock cord dock end into the boat with the cord plugged into the
boat and measure resistance between the ground pin on the dock plug and
the engine block. I, personally, think there should be NO connection
between the dock ground pin and the engine block through the battery
charger. That will start an interminable argument about safety, but I'm
willing to stick my neck out in the name of zinc survival. The battery
charger's DC circuit shouldn't be connected to dock ground because that
will form a huge battery because the dock ground is GROUNDED! You now
have a shorted battery formed between the bottom of the ocean the dock
ground is connected to and the prop shaft with the ocean as
electrolyte....eating the zinc. If the engine block is NOT connected to
the dock ground pin, current cannot flow through it eating the zinc.
The only current, then, would be the battery formed by the shaft/prop
steel/brass/potmetal and the zinc, a much, much smaller battery current
eating the zinc.

So since I have no shore power, could the bilge switch itself be eating
up a whole zinc within six months? There seems to be an unexplained
drain of the batteries also.

The other important test uses the ammeter of the digital voltmeter or
analog VOM. Leave the dock cord unplugged from the dock, but plugged
into the boat. plug one lead from the DC ammeter into the dock socket
GROUND socket. If you're not absolutly sure which that is...DO NOT DO
THIS TEST. TOUCHING THE HOT AC POWER MAY CAUSE PERSONAL INJURY. Turn
off the dock breakers before doing this test, anyways, as it doesn't
unconnect ground.

Now, with the DC milliameter connected to the dock ground, touch the
other lead to the boat ground. The current should be ZERO DC CURRENT.
If you see a measurable DC current flowing to/from the dock ground,
there's your zinc problem....the zinc is protecting the entire
electrical system of the local power company all the way back to the
generator house! This is NOT good.....

Sometimes the ONLY cure is an isolation transformer that completely DC
isolates the boat from the dock electrical system, the best solution for
cruisers going overseas. The little diode isolators work ONLY if there
is no leaking AC power in the system. If you've ever looked under a
marina dock, you know the chance of that is damned near Zero. Those
half-eaten conduits drooping into the seawater, flooded to the core,
will never get fixed unless it blows the main breakers or makes a dock
transformer explode in the night.

Thanks for the help Larry, but what if I have no shore power?

Stephen

brian whatcott wrote:
On 7/20/2010 10:10 PM, Stephen Trapani wrote:
I lost a zinc on my prop shaft very quickly. My boat is moored with only
one other boat within miles. The only possible source on my boat (I
think) is the bilge switch in my bilge because it is the only thing on.
The connection to the switch is out of the bilge water, so it can only
be coming from the switch itself. I have a voltmeter. Is there any easy
way to test to see if the switch is leaking current?

Here's a quicky check: with no connection to shore power at all, find a
meter with a sensitive current scale like 50 microamps. Find a lighting
cord and connect the two wires at one end to the battery terminals. At
the bilge, connect one battery lead to the meter and dangle the other
meter lead in the water, preferably though a scrap of stainless sheet.
Check the reading.
Now connect the meter lead to the OTHER battery lead and dangle the
other meter lead in the bilge again. If you normally leave the boat
connected to shore power, repeat these two steps with shore power
reconnected.

Not a complete check, but it can catch many leaks.

My apologies, but I don't understand. If I have both leads connected to
the positive and negative battery terminals on one side, which one do I
hook to the meter and which do I dangle in the water, and how would
there then be one dangling from the meter into the water?

Stephen

Thanks for the replies. Sorry, I was unclear. My boat is on a hook,
miles from any marina, with only one boat on another hook a hundred
yards away. To the best of my knowledge, he has no issues with his
zincs. My battery switch is off, with the bilge switch being the only
thing powered on the entire boat. This bilge switch in the bilge is new
within the last year. The connection to it is out of the bilge water.

A salvage guy who does work for me said it could be the bilge switch
eating away my zincs. Does this seem feasible? Larry and Brian, should I
still follow your recommended tests considering the above?

Stephen

On 7/21/2010 9:20 PM, Stephen Trapani wrote:
brian whatcott wrote:
On 7/20/2010 10:10 PM, Stephen Trapani wrote:
I lost a zinc on my prop shaft very quickly. My boat is moored with only
one other boat within miles. The only possible source on my boat (I
think) is the bilge switch in my bilge because it is the only thing on.
The connection to the switch is out of the bilge water, so it can only
be coming from the switch itself. I have a voltmeter. Is there any easy
way to test to see if the switch is leaking current?

Here's a quicky check: with no connection to shore power at all, find
a meter with a sensitive current scale like 50 microamps. Find a
lighting cord and connect the two wires at one end to the battery
terminals. At the bilge, connect one battery lead to the meter and
dangle the other meter lead in the water, preferably though a scrap of
stainless sheet. Check the reading.
Now connect the meter lead to the OTHER battery lead and dangle the
other meter lead in the bilge again. If you normally leave the boat
connected to shore power, repeat these two steps with shore power
reconnected.

Not a complete check, but it can catch many leaks.

My apologies, but I don't understand. If I have both leads connected to
the positive and negative battery terminals on one side, which one do I
hook to the meter and which do I dangle in the water, and how would
there then be one dangling from the meter into the water?

Stephen

That procedure looks for leakage current from one battery terminal into
the bilge water, then from the other battery terminal into the bilge water.
To elaborate a little.
If you first connect the positive battery terminal to the meter, it
would be the positive meter lead to the positive battery terminal
and the negative meter lead into the bilge water. This would look for
leakage from a positive lead into say a sump pump, where the negative
battery lead is grounded.

Then connect just the negative battery terminal to the negative lead of
the meter, and dangle the positive meter lead in the bilge water.
This looks for leakage from a negative power lead, where the positive
battery terminal is grounded.

It goes without saying, that you don't disconnect any other lead from
the battery, while you do these two checks.

THEN, you could lift off ALL connections to one battery terminal and
connect the meter on some medium current range to measure the current
flowing from the battery into all the leads you took off (now connected
together).

I imagine you expect the standing current out of the battery to be zero.
Or do you? :-)

Good luck

Brian W

On 7/21/2010 9:21 PM, Stephen Trapani wrote:
Thanks for the replies. Sorry, I was unclear. My boat is on a hook,
miles from any marina, with only one boat on another hook a hundred
yards away. To the best of my knowledge, he has no issues with his
zincs. My battery switch is off, with the bilge switch being the only
thing powered on the entire boat. This bilge switch in the bilge is new
within the last year. The connection to it is out of the bilge water.

A salvage guy who does work for me said it could be the bilge switch
eating away my zincs. Does this seem feasible? Larry and Brian, should I
still follow your recommended tests considering the above?

Stephen


The best plan is:
first do the tests.
THEN form the theories! :-)

Tests cost nothing.

Brian W

Stephen Trapani wrote in news:JTN1o.45739
:

So since I have no shore power, could the bilge switch itself be eating
up a whole zinc within six months? There seems to be an unexplained
drain of the batteries also.



Assuming the negative terminal of the batteries is connected to the block
of the engine, most are, AND if there is ANY leakage path between the
positive terminal of the batteries to the sea, yes, it'll gobble up the
zincs in no time....sometimes eating the prop, rudder, other underwater
metals connected to DC ground inside the boat.

When you say "bilge switch" are you referring to the bilge pump float
switch?



--
iPhone 4 is to cellular technology what the Titanic is to cruise ships.

Larry

Larry wrote:
Stephen Trapani wrote in news:JTN1o.45739
:

So since I have no shore power, could the bilge switch itself be eating
up a whole zinc within six months? There seems to be an unexplained
drain of the batteries also.



Assuming the negative terminal of the batteries is connected to the block
of the engine, most are, AND if there is ANY leakage path between the
positive terminal of the batteries to the sea, yes, it'll gobble up the
zincs in no time....sometimes eating the prop, rudder, other underwater
metals connected to DC ground inside the boat.

When you say "bilge switch" are you referring to the bilge pump float
switch?

Yes.

Stephen