Yamaha 9.9 GMHS Troubleshooting
| Engine Model: Yamaha 9.9 GMHS |
| Engine Type: 2-stroke 2-cylinder short shaft gasoline outboard engine |
| Total Displacement: 15 cu.in (246 cc) |
| Rated Engine Power: 9.9 Hp (7.3 kW) at 5500 rpm |
| Fuel System: Carburetor |
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| Engine difficult to start or doesn't start |
Empty gas tank - Add gasoline.
Wrong fuel grade - Use correct gasoline grade.
Air or water in fuel system - Remove water or air from fuel system.
Spark plug wiring connection is damaged - Inspect the spark plug wire connection, replace or repair.
Spark plug is defective - Change spark plug as required.
Clogged fuel filter - Replace or clean fuel filter.
Carburetor is not adjusted - Check carburetor float adjustment.
Dirty fuel lines - Fuel lines must be clean.
Fuel tank air vent clogged or closed - Open or service air vent.
Fuel pump pressure is low - Repair or change fuel pump.
Reed valve is worn or damaged - Replace reed valve.
| Engine starts and stops suddenly |
Spark plug is defective - Spark plug need to be replaced.
Clogged or defective carburetor - Clean or install new carburetor.
Ignition coil is defective - Replace ignition coil as necessary.
Closed or restricted fuel tank air vent - Open or service air vent.
Fuel pump pressure is low - Change or rebuild fuel pump.
Ignition system failure - Test ignition and replace failed parts.
Fuel pump is damaged or dirty - Inspect fuel pump and change as required.
Carburetor malfunction - Check and repair as required.
Dirty fuel lines - Fuel lines need to be cleaned.
Fuel tank air vent clogged or closed - Open or service air vent.
Fuel filter is clogged - Change fuel filter.
Gaskets are damaged - Install new gaskets.
Engine is under excessive load - Load reducing is recommended.
Too lean carburetor mixture - Use proper settings.
Ignition timing is wrong - Set the ignition timing correctly.
Faulty thermostat - Change thermostat.
Defective water pump - Replace water pump.
Propeller selection improperly - Replace propeller.
Damaged or bent propeller - Replace propeller.
Outboard engine is positioned too low or too high - Mount the motor as required.
| Engine knocking sound or abnormal noise |
Low octane fuel - Change fuel.
Engine is running overloaded - Reduce engine load.
Low idle speed set incorrectly - Adjust as required.
Dirty or defective fuel pump - Clean or install new fuel pump.
Main bearings or crankshaft wear - Have bearings or crankshaft replaced.
Damaged piston rings or cylinder bore - Change defective parts.
Improperly or clogged carburetor - Clean or correctly adjust carburetor.
Clogged or defective fuel pump - Clean or replace fuel pump.
Ignition system problems - Inspect ignition system and change failed components.
Damaged gaskets - Install new gaskets.
Faulty powerhead components - Change defective components.
Propeller pitch or diameter incorrect - Replace propeller.
Damaged or improper size of propeller - Replace propeller.
Motor mounted at incorrect height on transom - Check the outboard engine mounting height.
Trim angle is incorrect - Adjust trim angle correctly.
| Engine using too much gasoline |
Carburetor main jet is improperly adjusted - Adjust it correctly.
Faulty or loose spark plug - Tighten or change the spark plug.
Worn sleeve, rings, or piston - Replace faulty components.
| Excessive engine vibration |
Propeller bent or damaged - Replace propeller.
Propeller shaft malfunction - Have propeller shaft replaced.
Weeds in the propeller - Remove weeds from propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Damaged or loose steering pivot Tighten or replace.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
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| Industrial Engines Technical Specifications |
