Yamaha F8CMH Troubleshooting
| Engine Model: Yamaha F8CMH |
| Engine Type: 4-stroke 2-cylinder SOHC gasoline outboard engine |
| Total Displacement: 11.9 cu.in (197 cc) |
| Rated Engine Power: 8 Hp (5.9 kW) at 6000 rpm |
| Fuel System: Carburetor |
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| Engine starts hard or will not start |
Empty fuel tank - Add fuel.
Wrong grade of gasoline - Use correct gasoline grade.
Fuel system clogged - Repair or replace.
Damaged spark plug wiring connection - Inspect the spark plug wire connection, replace or repair.
Defective spark plug - Spark plug need to be replaced.
Plugged fuel filter - Fuel filter needs changing.
Carburetor malfunction - Check and repair as required.
Fuel lines are clogged - Fuel lines must be clean.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Fuel pump defective - Replace or repair fuel pump.
Throttle cable is adjusted incorrectly or damaged - Change cable or adjust correctly.
Valve clearance is improper - Need to adjust valve clearance.
Valve timing is wrong - Set the valve timing properly.
| Engine starts and immediately shuts off |
Defective spark plug - Spark plug need to be replaced.
Clogged or defective carburetor - Replace or service carburetor.
Damaged ignition coil - Ignition coil should be replaced.
Fuel tank air vent clogged or closed - Fuel tank air vent need to be opened or cleaned.
Fuel pump defective - Replace or rebuild fuel pump.
Choke system is damaged - Check and repair choke system.
Valve clearance is improper - Adjustment procedure required.
Wrong valve timing - Set the valve timing properly.
Loose or broken valve springs - Install new valve springs.
Stuck valves - Valves must be cleaned.
Defective ignition system - Inspect ignition system and change failed components.
Fuel pump is clogged or faulty - Test fuel pump and replace if necessary.
Carburetor is not working properly - Inspect and adjust.
Restricted fuel lines - Service fuel lines.
Fuel tank air vent closed or restricted - Open or service air vent.
Clogged fuel filter - Fuel filter needs changing.
Damaged gaskets - Replace gaskets.
Water intake screen is dirty - Need to wash or clean.
Faulty choke system - Inspect and replace choke system components.
Engine overloaded - Reduce load.
Too lean fuel mixture in carburetor - Adjust carburetor correctly.
Ignition timing is wrong - Set the ignition timing correctly.
Thermostat is defective - Replace thermostat.
Water pump failure - Replace water pump.
Propeller selection improperly - Replace propeller.
Damaged or improper size of propeller - Replace propeller.
Outboard motor is mounted too high or too low - Mount the motor as required.
Engine oil insufficient - Checking oil level and add if necessary.
Damaged oil pump - Change oil pump as required.
Water intake is blocked - Clean and wash as required.
Wrong valve setting - Adjust valves correctly.
| Engine knocking sound or abnormal noise |
Low octane gasoline - Change gasoline.
Engine is running overloaded - Reduce engine load.
Low idle speed adjustment is incorrect - Adjustment required.
Dirty or damaged fuel pump - Check fuel pump and replace if necessary.
Crankshaft or main bearings are worn out - Need to install new components.
Cylinder bore or piston rings are damaged - Replace defective components.
| Engine power is insufficient |
Carburetor is incorrectly adjusted or clogged - Clean or properly adjust carburetor.
Fuel pump is clogged or faulty - Service or replace fuel pump.
Ignition system malfunction - Test ignition and replace failed parts.
Cylinder head gasket is worn - Install new head gasket.
Faulty powerhead components - Replace defective parts.
Burned or stuck valves - Service or change valves.
Incorrect propeller selection - Replace propeller.
Damaged or improper size of propeller - Replace propeller.
Outboard motor mounting height is set incorrectly - Have motor adjusted to proper transom height.
Incorrect trim angle - Adjust trim angle correctly.
| Excessive fuel consumption |
Carburetor main jet adjustment is incorrect - Adjust the carburetor main jet properly.
Loose or defective spark plug - Tighten or replace spark plug.
Worn sleeve, rings, or piston - Change faulty components.
| Motor vibrates excessively |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft damaged - Replace propeller shaft.
Weeds wraped around propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten bolt.
Steering pivot is loose or damaged Tighten or replace.
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