Starter Relay; Starting Circuit Overload Protection; Battery Cables For Mercruiser Models - Mercury MerCruiser Service Manual

3. Across the closed solenoid contacts to the starter motor windings
NOTE: With the starter motor windings energized, its attached gears engage with the flywheel, cranking the engine.
4. From the starter motor windings to the starter casing; and then through the starter motor mounting bolts to engine ground
5. From the engine ground to the negative (–) post of the battery (black battery cable)

Starter Relay

The starter relay is located on the port side of the engine, next to the PCM. For details on removing and testing the starter
relay, refer to PCM 112 Service Manual—Section 3A ‑ Component Testing.

Starting Circuit Overload Protection

Two devices provide circuit protection for the starting circuits.
1. The 50‑amp circuit breaker located on top of the engine on the PCM relay bracket. This circuit breaker protects the
components and wiring in the starter solenoid circuit.
2. A 90‑amp fuse, located next to the hot stud on the back side of the engine, which protects the engine wiring harness.
a
For additional details, refer to Section 4E ‑ Electrical System Overload Protection.

Battery Cables for MerCruiser Models

IMPORTANT: The OEM or designer of the vessel is responsible for selecting the proper battery cable size to replace the
minimum size listed in the Circuit Length and Cable Size table, if the cables are used for electrical loads in addition to cranking
the engine.
IMPORTANT: Use only copper battery cables. Do not use aluminum cables for marine installations.
IMPORTANT: Terminals must be soldered to the cable ends to ensure good electrical contact. Use only electrical‑grade (rosin
flux) solder. Do not use acid flux solder, as it may cause corrosion and a subsequent failure.
NOTE: Engine starting batteries should be located as close to the engine as possible.
See the following figure for correctly sizing cables. If longer battery cables are required, the cable size (gauge) must increase.
Circuit length is calculated by adding the total length of the positive (+) cranking circuit to that of the negative (–) cranking circuit
(positive battery post to negative battery post).
Use the same cable size for both positive and negative cables.
90-8M0099748 eng DECEMBER 2015
a - 90‑amp fuse
b - Hot stud
b
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a
b
a -
b -
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© 2016 Mercury Marine
Starting System
Wire size by cross‑sectional
area (gauge)
Battery cable length
Page 4A-7