Corrosion Protection; Internal Components; Removal - Mercury 1.7 MI Manual

SECTION 5
CE532

Corrosion Protection

Whenever two or more dissimilar metals are submerged in a conductive solution, such as
saltwater, polluted water or water with a high mineral content, a chemical reaction takes
place causing electrical current to flow between metals. The electrical current flow causes
the metal that is most chemically active, or anodic, to erode. This is known as galvanic
corrosion and, if not controlled, it will in time cause the need for replacement of power
package components exposed to water. Refer to the Marine Corrosion Protection Guide
(90-88181301).

Internal Components

There are anodes as part of the intercooler and heat exchanger systems, which serve as
sacrificial anodes.
These sacrificial anodes are installed in the seawater circuit to help avoid galvanic corrosion
caused by seawater.
Sacrificial anode locations:
• Front and rear of the heat exchanger.
• Two on the intercooler.

REMOVAL

1. Allow the engine to cool.
When removing anode plugs, close seacock, if equipped. If boat is not equipped
with a seacock, remove and plug seawater inlet hose to prevent a siphoning action
that may occur, allowing seawater to flow from the anode plug holes.
2. With engine off, close seacock (if equipped) or remove and plug seawater inlet hose if
no seacock exists.
3. Remove anode plugs and sacrificial anodes.
Typical
CMD-3967823 / 90-865237030 OCTOBER 2003
INDEX
a
77334
c
a - Front heat exchanger anode
b - Rear heat exchanger anode
CAUTION
77122
c - Intercooler anodes
d - Anode plug and sacrificial anode
MAINTENANCE
b
77304
d
71368
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