Stray Current Corrosion; Galvanic Corrosion; Corrosion Prevention - Four winns Horizon 210 Owner's Manual

H - 7

STRAY CURRENT CORROSION

A. General
Electrically induced underwater corrosion occasionally
affects boats and their related components. This is re-
ferred to as “Stray Current Corrosion” and appears as
surface pitting or deterioration. Stray current corrosion
is the decomposition of chemical compounds by electric
current.
Stray current corrosion can be caused by the polarity of
the dockside wiring system of the boat being reversed
from the power source (reversed polarity) or surround-
ing boats, an improperly wired battery installation, other
boats that are in close proximity that have electrical power
leakages, or any other source close to the boat that has
electrical power leakage into the water. Stern drive units
are especially vulnerable to stray current corrosion.
Periodically inspect the drive components and thru-hull
fittings to determine if stray current corrosion damage
exists. If corrosion damage is found, determine and cor-
rect the cause of stray current to prevent further dam-
age. Consult an experienced marine electrician or con-
tact your Four Winns® dealer for assistance.
The use of some shore power battery chargers, while
the boat is in the water and the battery is connected to
the system, can cause stray current corrosion. Have an
experienced marine electrician review any battery
charger installation to ensure a stray current corrosion
problem will not develop. An improper battery connec-
tion is a common cause of stray current corrosion.
NOTICE
Use only “Coast Guard” approved battery charg-
ers. Consult your Four Winns® dealer for his
recommendations.
Corrosion is usually more prevalent in polluted or salt
water than in clean water. It is also more likely to occur
when dockage is in an area with steel piers, large metal
boats, or where shore power is in use.
Horizon & Sundowner
Owner’s Manual
06/00
B. Galvanic Corrosion
Galvanic corrosion results from a potential electrical dif-
ference existing between dissimilar metals immersed in
a conductive solution (e.g., salt water). If these metals
touch or are otherwise electrically connected, this po-
tential difference produces an electron flow between
them. The attack on the more active metal is usually
increased and the attack on the less active metal is de-
creased, as compared to when these metals are not
touching.
C. Corrosion Prevention
Anti-corrosion anodes are attached to the bottom of the
gimbal housing to prevent corrosion to your stern drive
and underwater parts. These anodes will be slowly
eroded away by galvanic action and require periodic in-
spection. Please refer to the section on “Anti-Corrosion
Anodes” in your engine manufacturer’s manual for ad-
ditional information. The engine manual is included in
the owner’s packet.
Section H
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