Stray Current Corrosion - Four winns SL Series Owner's Manual

H - 8

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 Corrosion" 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 the polarity
of the dockside wiring system of the boat being
reversed from the power source (re versed polarity) or
surrounding boats, an improp erly wired battery
installation, other boats that are in close proximity that
have electrical power leakag es, or any other source
close to the boat that has electri cal power leakage into
the water. Stern drive units are especially vulnerable
to stray current corrosion.
Periodi cally in spect the drive compo nents and thru-
hull fittings to determine if stray current corrosion
damage exists. If corrosion damage is found, deter-
mine and correct the cause of stray current to prevent
further damage. Consult an experienced 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 charg ers. Consult your Four Winns
Dealer for recommendations.
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-
Electrical Systems - Section H
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.
C. Corrosion Prevention
Anti-corro sion an odes are attached to the bottom of
the gimbal housing to prevent corrosion to your stern
drive and underwa ter parts. These anodes will be
slowly eroded away by galvanic action and require
periodic inspection. Please refer to the section on
"Anti-Corrosion Anodes" or "Corrosion and Corrosion
Protection" in your engine manufacturer's manual for
additional information. The engine manual is included
in the owner's packet.
Owner's Manual Page 72