Mercury 92-858058K01, Manual

Page: 119 / 150

Section 5 - Maintenance
90-879172181
eng
FEBRUARY 2011 Page 111
Corrosion and Corrosion Protection
The Causes of Corrosion
NOTICE
Washing the MerCathode assembly can damage components and lead to rapid corrosion. Do not use any cleaning equipment
such as brushes or high‑pressure washers to clean the MerCathode assembly.
Whenever two or more dissimilar metals (like those found on the drive) 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).
Corrosion Protection
These power packages have anodes as standard equipment to help protect them from galvanic corrosion under moderate
conditions.
The MerCathode System and sacrificial anodes will provide corrosion protection under normal usage. However, boats connected
to AC shore power require additional protection to prevent destructive low‑voltage galvanic currents from passing through the
shore‑power ground wire. A Quicksilver Galvanic Isolator can be installed to block the passage of these currents while providing
a path to ground for dangerous fault (shock) currents. Refer to the Diesel Parts and Accessories Guide (90‑892645008) or the
Mercury Accessories Guide (90‑420000009) for part numbers.
IMPORTANT: If AC shore power is not isolated from boat ground, the MerCathode System and anodes may be unable to handle
the increased galvanic corrosion potential.
Anodes and MerCathode System
Anodes help protect against galvanic corrosion by sacrificing their metal to be slowly eroded instead of the metal components on
the drive or vessel.
Corrosion protection for the drive is provided by sacrificial anodes installed on the trim tabs. Other sacrificial anodes may be
mounted on the vessel to ensure against corrosion of vessel components.
IMPORTANT: Replace the sacrificial anodes if they are eroded 50 percent or more.
Anodes and MerCathode System Locations
Description Location Figure
Trim tab anode
plates
Mounted on the trim tab
41251
The MerCathode system uses a reference electrode and an anode assembly to help protect against galvanic corrosion. The
MerCathode controller is mounted on the transmission.
The system should be tested to ensure adequate output. The test should be performed where the boat is moored, using the
Quicksilver Reference Electrode and Test Meter. For testing, contact a Cummins MerCruiser Diesel Authorized Repair Facility or
refer to the appropriate
Cummins MerCruiser Drive Service Manual
.