Corrosion On Underwater Parts With Mercathode Or Impressed Current Protection - Mercury BRAVO Service Manual

TROUBLESHOOTING
Corrosion On Underwater Parts, With MerCathode Or Impressed Current
Protection
DRIVE OVER-PROTECTED
Faulty MerCathode reference
electrode.
Faulty MerCathode controller.
Stray current corrosion (electrical
current leaves a metal conductor and
creates a path through the water).
Poor connection between the
MerCathode reference electrode lead
(BRN) and the "R" terminal on the
controller.
MerCathode system not functioning.
Page 1C-32
Cause
SERVICE MANUAL NUMBER 28
Special Instructions
Disconnect reference electrode lead
(BRN) from "R" terminal on controller.
Connect the lead to the positive (+)
terminal of a digital multimeter (set on
0-2000 millivolt scale). Connect the
negative (-) meter lead to the negative
(-) battery terminal. Note the meter
reading; then repeat the test with a
test silver/silver chloride reference
electrode held behind the drive. The
same reading should be obtained in
both cases. If not, replace the
reference electrode.
Check controller output. If the hull
potential indicates overprotection,
remove the reference electrode
lead from the controller. If the
controller is off (no impressed
current called for) the voltage
between the negative (BLK) and between the negative (BLK) and
the anode should be less than 1
volt. Measure amperage; with the
reference electrode disconnected,
the amperage between the negative on
the controller and the anode terminal
should be less than 1 milli-amp. Replace
the controller if needed.
Disconnect electrical components one
at a time and observe the multimeter
reading until you eliminate the high
reading. Correct the source of the
stray current.
Clean and/or tighten the connection.
Repair wiring as needed.
Check the fuse in the hot lead.
Check the battery.
Check for loose connections at
controller and battery.
Check the grounding wire between
the sterndrive and the controller.
90-863160 MAY 2000