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H - 11 STRAY CURRENT CORROSION
A. General
Electrically induced underwater corrosion occa sionally
affects boats and their related compo nents. This is
referred to as "Stray Current Corro sion" and appears
as surface pitting or deteri oration. Stray current
corrosion is the de composi tion of chemi cal com-
pounds by electric current.
Stray current corrosion can be caused by sur rounding
boats; an improp erly wired battery/char ger instal la tion
or other boats that are in close proximity which have
electrical power leakages. Stern drive units are
especially vulnerable to stray current corrosion.
Periodi cally in spect the engine compo nents to deter-
mine if corrosion damage exists. If stray current
corrosion damage is found, determine and correct the
cause of the stray current to prevent further damage.
Con sult an experi enced marine electrician or contact
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 electri cian review any battery
charger installation to ensure a stray cur rent corrosion
problem will not devel op. An improper battery connec-
tion is a com mon cause of stray cu rrent corrosion.
NOTICE
Use only UL Marine-ignition protected battery
charger(s) designed to meet US Coast Guard
regulations for external ignition protection.
Corrosion is usually more prevalent in polluted or salt
water than in fresh water. It is also more likely to occur
when dock age is in an area with steel piers, large
metal boats, or where shore power is in use.
B. Galvanic Corrosion
Galvanic corrosion results from a potential electri cal
difference existing between dissimilar metals im-
mersed in a conductive solu tion (e.g., salt or brackish
water). If these metals touch or are otherwise electri-
cally connected, this potential difference produces an
electron flow between them. The attack on the more
active metal is usually in creased and the attack on the
less active metal is decreased, as compared to when
these metals are not touching.
Electrical Systems - Section H
C. Corrosion Prevention
Anticorrosion an odes are attached to the transom
to prevent corrosion to your electrical systems and
underwa ter parts. These anodes will be slowly eroded
away by galvanic action and require periodic inspec-
tion. Please refer to the section on "Anti-Corrosion
Anodes" in your engine manufacturer's manual for
additional information.
Owner's Manual Page 86
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