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Mercury 90 Service Manual

Mercury 90
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3B-20 - FUEL SYSTEM 90-830234R3 DECEMBER 1997
Fuel System Troubleshooting
General Information
Problems that are thought to be caused by the fuel
system may, in reality, be something completely dif-
ferent. Items, that are shown below, could give the
impression that there is a problem in the fuel system.
1. Propeller
2. Spark Plugs
3. Ignition Timing
4. Ignition Spark Voltage
5. Cylinder Compression
6. Reed Valves
Typical symptoms and solutions in troubleshooting a
fuel system are shown below.
Problem: Engine Floods
Possible Cause Corrective Action
Dirt or debris are preventing inlet needle from seat-
ing
Flush out inlet seat and clean inlet needle
Worn inlet needle Replace
Punctured float Replace
Incorrect float setting Reset float
Problem: Engine Runs Too Rich
Possible Cause Corrective Action
Fuel level too high Reset float to correct level
Carburetor floods See preceding “Engine Floods”
Idle nozzle air holes plugged Blow out with compressed air
Restricted air flow Inspect cowl air inlet and carburetor for obstructions
Main fuel jet loose Re-tighten jet
Problem: Fuel Blow Back Out Of Carburetor
Possible Cause Corrective Action
Chipped or broken reeds on reed block Replace reeds
Problem: Rough Idle
Possible Cause Corrective Action
Excessive pre-load on reeds Replace reeds

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Mercury 90 Specifications

General IconGeneral
BrandMercury
Model90
CategoryOutboard Motor
LanguageEnglish

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