I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct electrical
contact on the boat will break down the weakest point of the aluminum and cause
holes in the boat. This is especially important if you are a SAL****ER Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or material."

How could you avoid this? The motor is bolted directly to the metal transom
and is grounded, there is contact there. I checked my aluminum boat with a VOM
and there is definately continuity between the boat and the motor. Whats the
difference in letting the motor ground to the boat and not the wiring? What am
I missing here?

"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct
electrical
contact on the boat will break down the weakest point of the aluminum and
cause
holes in the boat. This is especially important if you are a SAL****ER
Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or
material."

How could you avoid this? The motor is bolted directly to the metal
transom
and is grounded, there is contact there. I checked my aluminum boat with
a VOM
and there is definately continuity between the boat and the motor. Whats
the
difference in letting the motor ground to the boat and not the wiring?
What am
I missing here?



The amount of current the boat hull carries. I can get a ground from the
hull, but I run a large wire to a terminal block with ground and power.

"Calif Bill" wrote in message
ink.net...

The amount of current the boat hull carries. I can get a ground from the
hull, but I run a large wire to a terminal block with ground and power.



If cars and fancy car audio are any indication, this method (fat wire to
terminal block or battery) may also help reduce ignition noise on the radio.

The amount of current the boat hull carries. I can get a ground from the
hull, but I run a large wire to a terminal block with ground and power.

OK. I can get a ground anywhere too.
So are you saying that if everything is grounded seperately by a wire running
back to the battery it will flow through the wire and not the boat? Mine is
wired this way, but a lot of the electrical devices are mounted directly to the
aluminum and will work without the ground wire.

Is this because the wire has less resistance than the boat?

Is the object here to keep the current at a minimum, Im sure SOME of it will
always go through the hull just because of the motor and the electrical items
attached to the boat.

Is there anyway to test how much is going through the hull and what is
considered a safe level?

Well CC, what you are missing is an understanding of electrolysis.
Electrolysis is caused by dis-similar metals in contact with each other,
and
in the presence of a catalyst. (salt) It makes a sort of crude battery,
producing tiny amounts of electricity.

The electricity is made from stripping electrons from the "weakest" of
the
two metals. In this case, the aluminum of your hull. acting as an anode
to
the strongest metal (useually stainelss steel) acting as a cathode. This
has
the apparent effect of burning holes in the metal at the points of
highest
activity. Bronze items are electricaly neutral.

Electrolysis, otherwise known as galvanic corrosion, is especially bad
for
aluminum hulls, and will "burn" holes through the metal. Once burned
through, the hull is near useless, and, in general, cannot be safely
repaired. There are a couple of things you can do to minimize the effect
of
G.C.

1. Paint the hull with a good grade of zinc based primer, covered with
a
top coat of quality marine grade metal paint. This will isolate the
sal****er (catalyst) from the aluminum, and retard corrosion.

2. Install zinc (or magnesium for freshwater) anodes on both the motor
and
the hull. The anodes are sacrificial, and will decay in the presence of
galvanic current. They must be replaced annually or whenever they become
"crusty". DO NOT wait until the zincs are partially dissolved, as they
lose
their protective ability rapidly after the white "crust" forms. If you
are
the thrifty sort, save your old zincs for re-melting.

3. Bond the motor, hull and battery (-) side. Run a bonding strap or
wire
from the negative terminal of the battery to: motor block; motor mount,
hull, control panel, and any dissimilar metal on the hull. I.E.
stainless
steel Cleats, deck fittings, light fixtures, radios, stereos, or any
dis-similar metal where it contacts the hull. This will equalize any
stray
current in the boat and avoid "hot spots" where G.C. does its worst
work.

Zamack or chrome plated zinc cleats and fittings will deteriorate in
salt
water. If your boat is equipped with these fittings from the factory,
replace them.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum
boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct
electrical
contact on the boat will break down the weakest point of the
aluminum
and cause
holes in the boat. This is especially important if you are a
SAL****ER
Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or
material."

How could you avoid this? The motor is bolted directly to the metal
transom
and is grounded, there is contact there. I checked my aluminum boat
with a VOM
and there is definately continuity between the boat and the motor.
Whats the
difference in letting the motor ground to the boat and not the
wiring?
What am
I missing here?

The wire, being copper, has a much greater potential for carrying current
due to its electron shell. Electricity will always flow along the path of
least resistance. Bonding your boat with copper wire will reduce the points
of oppertunity for electrical conduction through the hull. It will also
equalize stray current electrolysis, and lessen damage to your hull. It is
especially important to make sure tramsmitters and antenna are properly
bonded.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
The amount of current the boat hull carries. I can get a ground from
the
hull, but I run a large wire to a terminal block with ground and power.

OK. I can get a ground anywhere too.
So are you saying that if everything is grounded seperately by a wire
running
back to the battery it will flow through the wire and not the boat? Mine
is
wired this way, but a lot of the electrical devices are mounted directly
to the
aluminum and will work without the ground wire.

Is this because the wire has less resistance than the boat?

Is the object here to keep the current at a minimum, Im sure SOME of it
will
always go through the hull just because of the motor and the electrical
items
attached to the boat.

Is there anyway to test how much is going through the hull and what is
considered a safe level?

Thanks Frank,

Is this just an issue in salt water?
I noticed most of the fasteners on my boat are stainless and it came that way
from the factory. I only use my boat in fresh water and its on the trailer 99%
of the time.

Corrosion from fresh water is also a problem, but no where near as severe
as salt water. say 15% or so. In fresh water use magnesium anodes on both
hull and motor. The dis-similar metals of stainless and aluminum will
generate galvanic corrosion when moisture is present. If you have a
stainless prop the problem is worse. Notice I said moisture. It can be from
simple humidity or fog or any other source. The reaction requires very
little water to initialize. It does make for a messy looking boat in a year
or 2. Anodes are cheap protection.
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"CCred68046" wrote in message
...
Thanks Frank,

Is this just an issue in salt water?
I noticed most of the fasteners on my boat are stainless and it came
that way
from the factory. I only use my boat in fresh water and its on the
trailer 99%
of the time.

It advised against using the hull as your negative return like they do for
cars where the chasis is used as the negative return.

If the hull is used, current flow through it will create potential
differences across joints and create points for electrolysis action which
will ultimately eat away the hull. Fresh or sal****er only changes the
severity and speed of the electrolytic action.

This is different from bonding where you want to create zero resistance
between metal parts, like the engine and the hull as you described where
there is already electrical contact, a bonding wire is used to
provide/improve the electrical bond. With zero resistance (I mean real
zero, not achieveable in real life) you can eliminate galvanic corrosion
which occurs when 2 dissimilar metals come into contact with each other.
The severity of this corrosion is a function of the 2 material and is
reduced by the effectiveness of the bond.

This corrosion can be diverted through the use of anodes (zinc/magnesium
anodes) where something else is sacrificed. Note that this does not stop
the corrosion, something else takes the brunt of it.

Tan PS


"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT. Direct
electrical
contact on the boat will break down the weakest point of the aluminum and
cause
holes in the boat. This is especially important if you are a SAL****ER
Boater.
This is called ELECTROLYSIS and is not a defect in workmanship or
material."

How could you avoid this? The motor is bolted directly to the metal
transom
and is grounded, there is contact there. I checked my aluminum boat with
a VOM
and there is definately continuity between the boat and the motor. Whats
the
difference in letting the motor ground to the boat and not the wiring?
What am
I missing here?

"Capt Frank Hopkins" wrote
Electrolysis, otherwise known as galvanic corrosion

Begging leave to differ, Capt Frank, but they're two different things. What
you're describing is galvanic action caused when dissimilar metals immersed
in an electrolyte decide to act like a battery and generate electric current
all by themselves. Electrolysis happens when an external source of
electrical current, like your starting battery or shore power supply,
generates electrical current through the water.