Mercathode System Battery Requirements; Mercathode Theory Of Operation; Power Package Exterior Surfaces - Mercury TDI 3.0L Owner's Operation And Maintenance Manual

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
Solid green No fault. The controller is working properly.
There is an open or short in the reference
2 flashes per electrode/anode, a high temperature, or a
second sensed reference electrode voltage in
excess of 1.4 V.
The reference voltage is outside of the
1 flash per 4
normal, expected range: either above 1.04 V
seconds
or below 0.86 V.
There is no power to the controller or both
LED not on
the reference electrode and anode are open.

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.
Corrosion Guard
120
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
Mercury Light Gray Primer
Mercury Phantom Black
Mercury Warm Fusion White
90-8M0145546 MAY 2018
eng
Definition
Description
Required Action
No action is necessary. This is the normal LED indication
for a properly functioning MerCathode system.
The system is not operating correctly. Contact your local
Mercury Service dealer for assistance.
The system is stabilizing. Monitor it for further change.
• 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.
Where Used
Painted surfaces
Section 4 - Maintenance
Part No.
92-802878 55
Part Number
92‑802878 52
92‑802878Q 1
8M0094987
Page 71