Low Readings - Mercury BRAVO Service Manual

SERVICE MANUAL NUMBER 28

Low Readings

Loss of continuity between sterndrive unit
components and negative (-) battery
terminal.
Shore power green safety grounding lead
not isolated from the power package
ground on boats equipped with shore
power.
Underwater metal parts on the sterndrive
unit and/or boat are unpainted or the paint
is in poor condition. The boat has more
exposed metal than the anodes and/or
MerCathode system can protect.
Anodes painted.
The anodes are improperly grounded or
inactive.
Anodes consumed (no longer protect).
Sterndrive unit and/or boat bottom painted
with anti-fouling paint containing copper or
tin.
MerCathode reference electrode or anode
painted.
Anodic heads used instead of plastic caps. Reinstall the plastic caps.
No power to MerCathode controller.
Poor connection between reference
electrode lead (brown) or anode lead
(orange) and MerCathode controller.
90-863160 MAY 2000
Cause
CORROSION PROTECTION - ALL MODELS
Special Instructions
Ensure that continuity devices are not
missing or damaged and that connections
are clean and tight.
Disconnect shore power and verify if
reading increases. If so, install a
Quicksilver Isolator P/N 18478A2 or an
isolation transformer.
Prime and paint underwater metal parts.
This will reduce the load on the anodes
and/or MerCathode system.
Remove paint or replace anodes.
Clean anode mounting surface or replace
anodes if they have oxidized.
Replace anodes if eroded 50% or more.
Avoid any electrical interconnection
between the MerCruiser product, anodic
blocks, or MerCathode system and the
paint by allowing a minimum of 1-1/2 in.
(40 mm) of UNPAINTED area around
these items on the transom of the boat.
Remove paint.
Connect the positive (+) volt meter lead
(set on 0-20 volt scale) to the positive (+)
controller terminal and the negative (–)
volt meter lead to the negative (–)
terminal. The meter should indicate
battery voltage. Check for a blown fuse (if
equipped) on the starboard MerCathode
system. Clean the connection or repair
wiring as required.
Clean and/or tighten the connection.
Repair the wiring.
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