Fuel System Troubleshooting; General Information; Problem: Engine Floods; Problem: Engine Runs Too Rich - Mercury 75 Service Manual

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
Dirt or debris are preventing inlet needle from seat-
ing
Worn inlet needle
Punctured float
Incorrect float setting

Problem: Engine Runs Too Rich

Possible Cause
Fuel level too high
Carburetor floods
Idle nozzle air holes plugged
Restricted air flow
Main fuel jet loose

Problem: Fuel Blow Back Out Of Carburetor

Possible Cause
Chipped or broken reeds on reed block

Problem: Rough Idle

Possible Cause
Excessive pre-load on reeds
3B-20 - FUEL SYSTEM
Corrective Action
Flush out inlet seat and clean inlet needle
Replace
Replace
Reset float
Corrective Action
Reset float to correct level
See preceding "Engine Floods"
Blow out with compressed air
Inspect cowl air inlet and carburetor for obstructions
Re-tighten jet
Corrective Action
Replace reeds
Corrective Action
Replace reeds
90-830234R3 DECEMBER 1997