Yamaha 9.9 FMHS Troubleshooting
| Engine Model: Yamaha 9.9FMHS |
| 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 hard to start or won't start |
Empty fuel tank - Add gasoline.
Wrong fuel grade - Use quality gasoline.
Air in fuel system - Bleed fuel system.
Spark plug wire is loose or disconnected - Check the spark plug wire connection, repair or replace.
Damaged spark plug - Spark plug need to be replaced.
Fuel filter is plugged - Fuel filter needs to be replaced.
Carburetor is not adjusted - Check carburetor float adjustment.
Dirt in the fuel lines - Clean fuel lines.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Low fuel pump pressure - Install new pump or repair it.
Reed valve is worn or damaged - Install new reed valve.
| Engine starts and stalls suddenly |
Spark plug is defective - Install new spark plug.
Carburetor is faulty or dirty - Service or change carburetor.
Ignition coil is faulty - Replace ignition coil as necessary.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Low fuel pump pressure - Install new pump or repair it.
Defective ignition system - Inspect ignition system and change faulty parts.
Clogged or damaged fuel pump - Clean or change fuel pump.
Carburetor is not working properly - Inspect and adjust.
Fuel lines are dirty - Fuel lines must be clean.
Fuel tank air vent closed or restricted - Open or clean air vent.
Fuel filter is plugged - Change fuel filter.
Gaskets are damaged - Change gaskets.
Engine is running overloaded - Reduce load.
Too lean carburetor mixture - Adjust carburetor correctly.
Ignition timing is wrong - Ignition timing needs to be adjusted correctly.
Thermostat is faulty - Install new thermostat.
Water pump failure - Change water pump.
Incorrect propeller selection - Replace propeller.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard motor is mounted too high or too low - Position the engine correctly.
Stale gasoline - Use proper fuel.
Engine is under excessive load - Reduce the load.
Wrong adjustment of low idle speed - Adjust idle speed.
Dirty or damaged fuel pump - Service or replace fuel pump.
Crankshaft or main bearings failure - Replace crankshaft or bearings.
Piston rings or cylinder bore are worn - Change defective parts.
| Engine power is insufficient |
Carburetor is dirty or incorrectly adjusted - Adjust the carburetor correctly or clean it.
Fuel pump is defective or dirty - Test fuel pump and change if necessary.
Defective ignition system - Check ignition and replace faulty components.
Damaged gaskets - Change gaskets.
Faulty powerhead components - Replace defective parts.
Propeller selection improperly - Check the propeller size.
Propeller bent or damaged - Replace propeller.
Motor mounted at incorrect height on transom - Check the outboard engine mounting height.
Trim angle is incorrect - Adjust trim angle.
| Engine using too much gasoline |
Incorrect carburetor main jet adjustment - Adjust main jet as required.
Spark plug is defective or loose - Replace or tighten spark plug.
Sleeve, rings, or piston are damaged - Change defective parts.
| Excessive motor vibration |
Propeller bent or damaged - Replace propeller.
Damaged propeller shaft - Replace propeller shaft.
Weeds clogs the propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Loose or faulty 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 |
