Regal LS4C Owner's Manual page 165

Typically electrons flow from the anode (the alumi-
num drive unit), via the external conducting path to
the cathode (stainless steel propeller). If there is
a very large anode connected to a small cathode,
the anode will corrode very slowly. If a very large
cathode is connected to a small anode, the anode
will corrode very quickly. Obviously, if you do not
control galvanic corrosion, over time the aluminum
will corrode away.
The first sign of galvanic corrosion is paint blis-
tering (starting on sharp edges) below the water
line- a white powdery substance forms on the ex-
posed metal areas. As the corrosion advances, the
exposed metal will become deeply pitted as the
metal is actually eaten away.
Another condition which will increase galvanic cor-
rosion is the removal or reduction in surface area of
the sacrificial anodes. Never add aftermarket prod-
ucts that are connected to the engine ground such
as stainless steel steering aids and trim planes.
Zinc connected to aluminum will form a corrosion
cell but the aluminum (drive) becomes the cathode
and the zinc (anode) corrodes.
Even though your boat may not have shore pow-
er aboard current from nearby vessels with shore
power can produce stray current galvanic corro-
sion. Stray current corrosion occurs when metal
with an electrical current flowing into it is immersed
in water that is grounded (lake, ocean, pond). The
current can leave the metal and flow through the
water to ground. This will cause rapid corrosion
of the metal at the point where the current leaves.
When a vessel nearby is plugged into shore pow-
er, they can potentially tie your drive unit to their
boat via the green grounding shore power lead.
Your drive unit could be the receiving end of a
large galvanic cell (a battery) interconnected with
nearby vessels or even through the marina's metal
structures via their electrical system.
The vessel should be tested every couple of weeks
to determine the integrity of the anode protection
system. Another way to test the system is to mea-
sure the hull potential. This is accomplished by im-
mersing a reference electrode, usually a silver/sil-
ver chloride into the water about six inches behind
the drive. With leads attached to a digital multi-
meter the hull potential is read on the DC scale
and compared to recommended specifications for
the water body type. See the owner's information
vendor packet for more information or contact your
nearest authorized Regal dealer.
Tips To Aid In Maintaining Galvanic Integrity
1. Test the galvanic integrity of your vessel every 2
weeks. Raise the drive and inspect anodes/parts
for signs of galvanic corrosion, stray current cor-
rosion or loose fasteners. Contact your closest
Regal dealer/marine professional where signs of
galvanic corrosion exist.
2. Never paint over anodes as they will become in-
operative. Always leave at least one inch between
bottom paint and any underwater fitting such as
sea cocks, swim platform stanchions and all drive
and propulsion related underwater parts.
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