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S
8.
E
LECTROLYTIC
Z
A
INC
NODES
Electrolytic corrosion of metals on power boats can
result in rapid and serious deterioration of metal
parts. You must set a regular schedule and look
for the possibility of electrolytic corrosion (the
deterioration of metals due to dissimilar
characteristics when placed in salt water). It is your
responsibility to check for and replace parts
damaged due to electrolytic corrosion.
To minimize electrolytic corrosion of the metals on
your boat, zinc anode plates are provided on your
boat to protect underwater hardware. Zinc, being
much less "noble" than the copper-based alloys and
aluminum used in underwater fittings, will deteriorate
first and protect the other metals.
Stern drives are fitted with zinc anodes on their lower
units (refer to your Engine Owner's Manual for their
locations). If your boat is equipped with trim tabs,
zinc plates are installed on each of the trim tabs.
(See Figure 6.9.1) If boat is equipped with
Mercathode
stern drive may not have zincs.
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Zinc anodes require replacement about every six
months, if the boat is operated in salt water. In fresh
water, the zinc anodes can be replaced about once
a year.
If the anodes deteriorate more rapidly than this, there
is probably a stray current problem within the boat
or at the slip or mooring.
If the anodes do not deteriorate, they are not
protecting the other metallic parts of your boat. This
can be caused by loose anodes or by low grade
zinc or by not having a solid electrical contact
between the anode and the metal it contacts, or by
paint on the anodes.
If the anodes are deteriorating rapidly, or not at all,
contact your dealer.
6.8
6 • E
ECTION
C
ORROSION AND
S
LECTRICAL
YSTEM
When an AC shore power system is connected to
the boat, the underwater metal fittings will, in effect,
be connected through the water to grounded metals
ashore. This results in the zincs being consumed
at a faster rate unless the marina maintains a
protective system to prevent this. When the marina
provides a zinc anode in the water bonded to the
metal outlet box on the dock, zinc loss on the boat
will be reduced. Do not connect this zinc to the
boat's ground system.
It is extremely important that all electrically-operated
DC equipment and accessories be wired so that the
ground polarity of each device is the same as that
of the battery. Your boat has a negative ground
system. The zinc anode is connected to every metal
item in the boat (fuel tanks, underwater gear, etc.)
via the green bonding wire.
Electrolytic corrosion can also be caused by "stray
currents" due to a fault in an electrical item, even
though correctly grounded. A galvanic current
isolator (zinc saver) is standard on all Sea Ray
boats. It is installed between the shore power ground
and the boats' AC grounding connection to the DC
bonding system. This connection maintains the
safety ground from dockside power while stopping
the flow of DC corrosive currents.
DO NOT PAINT BETWEEN THE ZINC AND THE
METAL IT CONTACTS, AND DO NOT PAINT OVER
THE ZINC.
Never disconnect the green wire (safety ground) from
the engine terminal.
NOTICE
!
CAUTION
240 Sundeck
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