Service manual

TROUBLESHOOTING
SERVICE MANUAL NUMBER 26
90-861329--1 MARCH 1999 Page 1C-21
Radio Noise
Cause Special Information
A popping noise that will increase with
engine rpm. Noise will stop as soon as
engine is turned off.
Ignition System - wrong spark plugs;
cracked distributor cap; cracked coil tower;
leaking spark plug wires; moisture on
ignition components
High pitched whine in the radio
Alternator - poor brush contact on the slip
rings
A hissing or crackling noise when
instruments are jarred with ignition on
Instrumentation - loose connections or
antennae wire routed too close to
instruments
Varying unexplained noises
Accessories - bilge pump, bilge blower;
fish finder; depth locator; cabin heater
motor, etc. Disconnect one at a time until
noise disappears.
Troubleshooting With Vacuum Gauge
Reading Cause
Steady reading between 15-21 inches at
idle rpm
Normal
Extremely low reading, but steady at idle
rpm
Vacuum leak; incorrect timing;
underpowered boat; faulty boat bottom
Fluctuates between high and low at idle
rpm
Blown head gasket between two adjacent
cylinders
Fluctuates 4 or 5 inches very slowly at idle
rpm
Carburetor needs adjustment; spark plug
gap too narrow; valves are sticking
Fluctuates rapidly at idle, steadies as rpm
is increased
Valve guides are worn
Continuously fluctuates between low and
normal reading at regular intervals at idle
rpm
Burned or leaking valve
Miscellaneous
Cause Special Information
Low grade or stale fuel
Water in fuel
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