PRODUCT OVERVIEW
12/05
ZT370 Operation Manual
13
CORROSION PROTECTION
Galvanic Corrosion
Galvanic corrosion results whenever two
or more dissimilar metals (like those found
on the stern-drive) are submerged in a
conductive solution, such as saltwater,
polluted water or water with a high mineral
content because a chemical reaction takes
place causing electrical current to flow
between the metals. The electrical current
flow causes the metal that is most
chemically active, or anodic, to erode. If
not controlled, galvanic corrosion may
corrode stern-drive components.
NOTICE
The anode of the stern-drive is only
calculated for the stern-drive. Changing
the material of the propeller may require
additional anodes to be installed on the
stern-drive.
Corrosion Control
It is the boat designer’s responsibility
and/or the re-powering engineer’s
responsibility to design the proper systems
and equipment to control and reduce the
possibility of galvanic corrosion.
To help control the effects of galvanic
corrosion, Yanmar Marine ZT370
stern-drives come with several anodes and
an electronic anticorrosion system
(Y-CaPS) that protect the stern-drive in
moderate corrosive conditions. However, it
is essential that the owner/operator
frequently monitor the anodes for wear,
inspect the stern drive for corrosion and
replace the anodes often enough to
provide a sacrificial surface for the
electrical current to attack. Galvanic
isolators are also available from the
aftermarket (not supplied by Yanmar) to
block stray current while still providing a
path to ground for dangerous shock
currents.
The rate of corrosion depends on
numerous factors, such as:
• The number, size and location of anodes
on the stern-drive and vessel;
• The marina environment such as stray
current in the water, fresh or salt water
and use and isolation of shore power;
• Improper application of marine paint or
antifouling paint;
• Failure to repaint damaged areas; and
• How the vessel is bonded.
Please check with the boat builder, dealer
or other professional to determine if your
vessel and/or stern drive is adequately
protected from galvanic corrosion.
If anodes erode quickly or if signs of
corrosion are evident, the owner should
take immediate corrective action. Yanmar
recommends consulting an engineer
specializing in marine electricity and
corrosion control to determine the best
way to correct the rapid erosion of the
anodes.
Shore Power
Vessels that are connected to shore power
require additional protection to prevent
destructive low voltage galvanic currents
from passing through the shore power
ground wire. Galvanic isolators are
available from the aftermarket (not
supplied by Yanmar) to block these
currents while still providing a path to
ground for dangerous shock currents.
NOTICE
If the AC shore power ground is not
isolated from the boat ground, the Y-CaPS
and anodes may be unable to neutralize
the increased galvanic potential. Corrosion
damage that results from the improper
system design or application is not
covered by the Yanmar limited warranty.
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