Yamaha 9.9 MSH Troubleshooting
| Engine Model: Yamaha 9.9 MSH |
| 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 starts up hard or doesn't start |
Gas tank is empty - Fill gasoline up.
Wrong grade of gasoline - Use quality gasoline.
Air in fuel system - Bleed fuel system.
Spark plug wire is disconnected or loose - Inspect spark plug wiring connection, change or repair.
Defective spark plug - Change spark plug as required.
Fuel filter is clogged - Fuel filter needs to be replaced.
Carburetor incorrectly set - Set carb correctly.
Fuel lines are clogged - Service fuel lines.
Closed or clogged fuel tank air vent - Open or service air vent.
Low fuel pump pressure - Install new fuel pump or rebuild it.
Worn or defective reed valve - Replace reed valve as required.
| Engine starts and stops suddenly |
Damaged spark plug - Change spark plug as required.
Carburetor is defective or clogged - Clean or replace carburetor.
Faulty ignition coil - Change ignition coil as required.
Closed or clogged fuel tank air vent - Open or service air vent.
Lack of fuel pump pressure - Repair or change fuel pump.
| Engine runs intermittently |
Ignition system problems - Inspect ignition system and change failed components.
Dirty or faulty fuel pump - Service or change fuel pump.
Carburetor incorrectly set - Set carb correctly.
Fuel lines clogging - Service fuel lines.
Fuel tank air vent clogged or closed - Fuel tank air vent need to be opened or cleaned.
Clogged fuel filter - Replace fuel filter.
Gaskets are damaged - Install new gaskets.
Engine is under excessive load - Load reducing is recommended.
Too lean fuel mixture in carburetor - Set the carburetor correctly.
Wrong ignition timing - Ignition timing needs to be set properly.
Damaged thermostat - Replace thermostat.
Defective water pump - Change water pump.
Propeller pitch or diameter incorrect - Replace propeller.
Propeller bent or damaged - Replace propeller.
Outboard motor is mounted too high or too low - Position the engine correctly.
| Abnormal engine noise or knocking |
Stale gasoline - Use proper gasoline.
Excessive engine load - Reduce the load.
Improperly adjusted low idle speed - Correct idle settings.
Fuel pump is damaged or dirty - Test fuel pump and change if necessary.
Main bearings or crankshaft wear - Need to install new components.
Damaged piston rings or cylinder bore - Replace defective components.
Carburetor is clogged or incorrectly adjusted - Adjust carburetor properly or service it.
Fuel pump is defective or dirty - Service or replace fuel pump.
Ignition failure - Check ignition and replace faulty components.
Worn gaskets - Change gaskets.
Worn powerhead parts - Change defective parts.
Incorrect propeller selection - Replace propeller.
Propeller bent or damaged - Replace propeller.
Motor mounted at incorrect height on transom - Have motor adjusted to proper transom height.
Trim angle is incorrect - Make the correct trim angle adjustment.
| Excessive fuel consumption |
Carburetor main jet adjustment is improper - Adjust it correctly.
Spark plug is loose or faulty - Replace or tighten spark plug.
Worn rings, piston, or sleeve - Replace faulty components as required.
| Motor vibrates excessively |
Damaged or bent propeller - Replace propeller.
Propeller shaft damaged - Replace propeller shaft.
Weeds in the propeller - Remove and clean propeller.
Engine mounting bolt is not tightened - Tighten bolt.
Damaged or loose steering pivot Tighten or replace.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
