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