Yamaha 20CM Troubleshooting
| Engine Model: Yamaha 20CM |
| Engine Type: 2-stroke 2-cylinder gasoline outboard engine |
| Total Displacement: 26.2 cu.in (430 cc) |
| Rated Engine Power: 20 Hp (14.7 kW) at 5500 rpm |
| Fuel System: Carburetor |
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| Engine starts up hard or will not start |
No fuel in fuel tank - Fill gasoline up.
Wrong grade of gasoline - Use quality gasoline.
Clogged fuel system - Remove clogging.
Defective wiring connection of spark plug - Inspect the spark plug wire connection, replace or repair.
Defective spark plug - Replace spark plug.
Plugged fuel filter - Replace or clean fuel filter.
Carburetor malfunction - Check and repair as required.
Fuel lines are clogged - Clean fuel system lines.
Fuel tank air vent restricted or closed - Open or clean air vent.
Lack of fuel pump pressure - Install new fuel pump or rebuild it.
Reed valve is defective or worn - Replace reed valve.
| Engine starts but then stalls |
Spark plug is damaged - Replace spark plug.
Faulty or dirty carburetor - Service or replace carburetor.
Ignition coil is damaged - Ignition coil must be replaced.
Fuel tank air vent restricted or closed - Fuel tank air vent need to be opened or cleaned.
Lack of fuel pump pressure - Install new pump or repair it.
Ignition system is defective - Inspect ignition system and change failed components.
Clogged or defective fuel pump - Service or change fuel pump.
Incorrect carburetor adjustment - Adjust carburetor idle mixture screw.
Clogged fuel lines - Clean fuel lines.
Fuel tank air vent restricted or closed - Open or clean air vent.
Plugged fuel filter - Install new filter.
Gaskets are worn - Replace gaskets.
Engine is running overloaded - Reduce engine load.
Carburetor fuel mixture is too lean - Make the correct settings.
Incorrect ignition timing - Ignition timing needs to be set properly.
Damaged thermostat - Install new thermostat.
Water pump malfunction - Water pump need to be replaced.
Propeller selection improperly - Replace propeller.
Propeller bent or damaged - Replace propeller.
Outboard engine is positioned too low or too high - Mount the motor as required.
| Abnormal engine knocking or noise |
Stale gasoline - Use correct gasoline.
Excessive engine load - Reduce load.
Too low idle RPM - Correct the settings.
Clogged or damaged fuel pump - Clean or install new fuel pump.
Main bearings or crankshaft wear - Change or repair worn components.
Piston rings or cylinder bore are damaged - Change defective components.
Carburetor is clogged or improperly adjusted - Adjust the carburetor correctly or clean it.
Dirty or defective fuel pump - Check fuel pump and change if required.
Ignition system problems - Test ignition and replace failed parts.
Gaskets are damaged - Install new gaskets.
Powerhead parts are worn out - Replace defective components.
Incorrect propeller selection - Replace propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Incorrect outboard motor mounting height - Check the outboard motor mounting height.
Improper trim angle - Adjust trim angle.
| Excessive fuel consumption |
Incorrect carburetor main jet adjustment - Adjust it properly.
Faulty or loose spark plug - Re-tighten or change the spark plug.
Worn piston, rings, or sleeve - Change faulty parts.
Damaged or bent propeller - Replace propeller.
Propeller shaft malfunction - Have propeller shaft replaced.
Weeds in the propeller - Remove weeds from propeller.
Engine mounting bolt is not tightened - Tighten bolt.
Steering pivot is loose or damaged Tighten correctly or replace.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
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| Industrial Engines Technical Specifications |
