1. Paint the power package.
2. Annually spray the power package components on the inside of the boat with Corrosion Guard to protect the finish from
dulling and corrosion. You may also spray external power package components.
3. Keep all lubrication points, especially the steering system, shift, and throttle linkages, well lubricated.
4. Flush the cooling system periodically, preferably after each use.
MerCathode System Battery Requirements
The Mercury MerCruiser MerCathode system requires a minimum battery charge of 12.6 volts at all times to maintain
functionality.
Boats equipped with a MerCathode system that use shore power, and are not run for a long period of time, must use a battery
charger to maintain a minimum battery charge of 12.6 volts or above.
Boats equipped with a MerCathode system that do not have access to shore power must be operated often enough to maintain
a minimum battery charge of 12.6 volts or above at all times.
MerCathode Theory of Operation
The MerCathode system provides corrosion protection by impressing a reverse blocking current that stops the destructive flow
of galvanic currents. The MerCathode controller will regulate output to maintain 0.94 volts at the reference electrode.
A constant LED indicates that the system is operating correctly. A flashing LED indicates that a fault has occurred, or that an
abnormal condition exists.
IMPORTANT: When a boat or new drive is first put into service, the LED may initially indicate that the protective current is not
being supplied through the MerCathode anode. This condition is normal, and, in such cases, the LED may flash for a period.
The light from the LED will become steady after the boat is moored for a period of eight hours without operation.
MerCathode LED Codes
MerCathode LED
Definition Required Action
Solid green No fault. The controller is working properly.
No action is necessary. This is the normal LED indication
for a properly functioning MerCathode system.
2 flashes per
second
There is an open or short in the reference
electrode/anode, a high temperature, or a
sensed reference electrode voltage in
excess of 1.4 V.
The system is not operating correctly. Contact your local
Mercury Service dealer for assistance.
1 flash per 4
seconds
The reference voltage is outside of the
normal, expected range: either above 1.04 V
or below 0.86 V.
The system is stabilizing. Monitor it for further change.
LED not on
There is no power to the controller or both
the reference electrode and anode are open.
• If the boat is out of the water, no action is
necessary.
• Check the battery voltage; it must be 9 V or higher.
• Check the 5‑amp fuse in the controller wire harness.
• If further assistance is required, contact your local
Mercury Service dealer.
Power Package Exterior Surfaces
1. Spray the entire power package at recommended intervals with Corrosion Guard. Follow the instructions on the can for
proper application.
Tube Ref No.
Description Where Used Part No.
120
Corrosion Guard Painted surfaces 92-802878 55
2. Clean the entire power package. External surfaces that have become bare should be repainted with the recommended
primer and spray paint at recommended intervals.
Description
Part Number
Mercury Light Gray Primer 92‑802878 52
Mercury Phantom Black 92‑802878Q 1
Mercury Warm Fusion White 8M0094987
Section 4 - Maintenance
90-8M0145546 eng MAY 2018 Page 71
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