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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 ZT350 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.
Underwater Drive Coating
The lower gear case coating may be
damaged when hit by objects in the water,
or when having deposits removed from it.
The underwater coating must be inspected
at least once per year and when it is believed
that an object was hit that may have caused
damage. Repair and repaint damaged
areas immediately.
PRODUCT OVERVIEW
14
ZT350 Operation Manual
© 2008 Yanmar Marine International