Noisy Alternator; Instrumentation Malfunction; Radio Noise - Mercury MerCruiser MCM 454 Mag MPI Service Manual

TROUBLESHOOTING

Noisy Alternator

Loose mounting bolts
Drive belt
Loose drive pulley
Worn or dirty bearings
Faulty diode trio or stator

Instrumentation Malfunction

Faulty wiring, loose or corroded terminals
Faulty key switch
Faulty gauge
Faulty sender

Radio Noise

A "popping" noise that will increase with
engine rpm. Noise will stop as soon as en-
gine is turned off.
"High pitched whine" in the radio
A "hissing or crackling" noise when instru-
ments are jarred with ignition on
Varying unexplained noises
Index Index
Page 1C-12
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Cause
Cause
Cause
SERVICE MANUAL NUMBER 23
Special Information
Worn, frayed, loose
Special Information
Test, as outlined in SECTION 4D
Test, as outlined in SECTION 4D
Test, as outlined in SECTION 4D
Special Information
Ignition System - wrong spark plugs;
cracked distributor cap; cracked coil tower;
leaking spark plug wires; moisture on
ignition components
Alternator - poor brush contact on the slip
rings
Instrumentation - loose connections, or
antennae wire routed too close to instru-
ments
Accessories - bilge pump, bilge blower;
fish finder, depth locator; cabin heater
motor, etc. Disconnect one at a time until
noise disappears.
90-861326--1 MARCH 1999