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Charging and Starting System
2.
The battery is fully charged when, over a two hour period at a low charging rate (in amperes), all cells are gassing freely
(not spewing liquid electrolyte), and no change in specific gravity occurs. Full charge specific gravity is 1.260–1.275,
corrected for electrolyte temperature with electrolyte level at 4.8 mm (3/16 in.) over plate, unless electrolyte loss has
occurred (from age or overfilling), in which case, specific gravity reading will be lower. For most satisfactory charging, lower
charging rates in amperes are recommended.
3.
If, after prolonged charging, specific gravity of at least 1.230 on all cells cannot be reached, battery is not in optimum
condition and will not provide optimum performance; however, it may continue to provide additional service, if it has
performed satisfactorily in the past.
4.
To check the battery voltage while cranking the engine with an electric starting motor at ambient air temperature of 23.8 °C
(75 °F), place the red (+) lead of the tester on the positive (+) battery terminal and the black (–) lead of the tester on the
negative (–) battery terminal. If the voltage drops below 10‑1/2 volts while cranking, the battery is weak and should be
recharged or replaced.

Fuses

Fuses protect the electrical circuits on the outboard from overload. If a fuse is open, try to locate and correct the cause of the
overload. If the cause is not found, the fuse may open again.
1.
Remove the top cowl. Locate the fuse holder on the port side of the engine.
2.
Remove the plastic cover from the fuse holder.
3.
Remove the suspected open fuse to determine if the metal band is broken.
4.
If necessary, replace the fuse with a new fuse of the same amperage rating.
d
c
b
a
Page 6B-4
e
f
g
h
© 2018 Mercury Marine
i
k
j
64390
63317
a -
Ignition coils—20 amp
b -
Oxygen sensor—10 amp
c -
Fuel pump—20 amp
d -
Diagnostics—2 amp
e -
Fuel injectors—20 amp
f -
Advanced sound control—5 amp (not
used on all models)
g -
Driver power—20 amp (start relay, fuel
pump relay, PCM drivers)
h -
TVM power—15 amp (not used on all
models)
i -
Spare fuses (3)
j -
Good fuse
k -
Open fuse
90-8M0146617 eng JULY 2018

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