Tohatsu MFS15E Troubleshooting
| Engine Model: Tohatsu MFS15E |
| Engine Type: 4-stroke 2-cylinder SOHC gasoline outboard engine |
| Total Displacement: 20.3 cu.in (333 cc) |
| Rated Engine Power: 15 Hp (11 kW) at 6000 rpm |
| Fuel System: Fuel Injection |
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| Engine difficult to start or won't start |
Fuel tank is empty - Fill fuel up.
Wrong grade of gasoline - Use quality fuel.
There is air in the fuel system - Bleed the system.
Defective wiring connection of spark plug - Inspect spark plug wiring connection, change or repair.
Spark plug is faulty - Change spark plug.
Fuel filter is dirty - Install new filter.
Worn or damaged vapor separator needle valve - Change vapor separator needle valve.
Restricted fuel lines - Clean fuel lines.
Fuel tank air vent clogged or closed - Open or service air vent.
Fuel feed pump defective - Fuel feed pump need to be replaced.
Choke cable is not adjusted properly or worn - Replace cable or adjust properly.
Excessive valve clearance - Check and adjust.
Valve timing is wrong - Set the valve timing correctly.
Low fuel pressure - Check system for fuel leaks or check low pressure fuel pump.
Clogged or worn fuel injector - Clean or install new injector.
Fuel regulator malfunction - Replace fuel regulator.
ECM is faulty - Change electronic control modul.
| Engine starts and then stalls |
Defective spark plug - Change spark plug as required.
Damaged or wear vapor separator needle valve - Replace needle valve.
Defective ignition coil - Ignition coil must be replaced.
Fuel tank air vent closed or restricted - Open or service air vent.
Fuel pump defective - Install new fuel pump or rebuild it.
Faulty choke system - Check and repair choke system.
Valve clearance is wrong - Adjust to proper valve clearance.
Improper valve timing - Adjust valve timing correctly.
Weak or damaged valve springs - Replace valve springs.
Valves are stuck - Valves must be cleaned.
Low cylinder compression - Check and change damaged parts.
Fuel filter is dirty - Install new filter.
Damaged or clogged fuel injector - Clean or replace if necessary.
Lack of engine oil - Check and refill engine oil.
Faulty oil pump - Change oil pump.
Water intake screen is dirty - Wash or clean as required.
Faulty thermostat - Install new thermostat.
Defective water pump - Replace water pump.
Ignition system is defective - Check ignition and replace faulty components.
Clogged or damaged fuel pump - Test fuel pump and change if necessary.
Damaged or wear vapor separator needle valve - Install new needle valve.
Fuel lines are dirty - Service fuel lines.
Fuel tank air vent clogged or closed - Open or service air vent.
Dirty fuel filter - Fuel filter needs to be replaced.
Intake manifold air leaks - Change intake manifold gasket.
Clogged water intake - Clean and wash as required.
Throttle valve and throttle link are damaged or worn - Change faulty components.
Fuel injector is damaged or dirty - Replace or clean if necessary.
Engine is under excessive load - Reduce load.
Fuel pump or fuel injector is clogged - Clean or replace as required.
Improper ignition timing - Adjust ignition timing as required.
Thermostat failure - Install new thermostat.
Water pump is defective - Change 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 level is insufficient - Add oil to the engine crankcase.
Oil pump malfunction - Replace oil pump.
Clogged water intake - Wash or clean as required.
Incorrect valve setting - Valves needs to be set correctly.
Stale gasoline - Use proper gasoline.
Excessive engine load - Load reducing required.
Low idle speed setting is not correct - Test and adjust.
Fuel pump is damaged or dirty - Check fuel pump and change if required.
Main bearings or crankshaft are worn out - Worn parts replacement required.
Worn piston rings or cylinder bore - Change defective components.
| Engine power is insufficient |
Restricted fuel lines - Clean fuel system lines.
Damaged fuel injector - Test fuel injector and change if necessary.
Dirty or damaged fuel pump - Test fuel pump and replace if necessary.
Ignition system failure - Inspect ignition system and change faulty parts.
Blown cylinder head gasket - Cylinder-head gasket replacement required.
Worn powerhead parts - Replace defective parts as required.
Stuck or burned valves - Replace or service valves.
Propeller selection improperly - Check the propeller size.
Damaged or bent propeller - Replace propeller.
Motor mounted at incorrect height on transom - Have motor adjusted to proper transom height.
Trim angle is incorrect - Adjust trim angle correctly.
Fuel injector is clogged or malfunction - Replace or clean if necessary.
Faulty or loose spark plug - Re-tighten or replace spark plug.
Worn rings, piston, or sleeve - Replace faulty components as required.
ECU failure - Replace ECU.
Damaged or bent propeller - Replace propeller.
Propeller shaft damaged - Have propeller shaft replaced.
Weeds wraped around propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten bolt.
Loose or faulty steering pivot Tighten or replace.
Low battery voltage - Low battery charging, charge as required.
Battery is not holding charge - Battery needs to be serviced or replaced.
Battery terminals are corroded or wires are disconnected - Check cable connections and replace or service terminals.
Starter motor is damaged - Repair or change starter.
| Trim motor is running but trim system cannot move up or down |
Insufficient oil - Need to add the oil.
Pump assembly faulty - Check pump and change if required.
Leakage of manual drain valve - Close the valve or change it.
Broken motor or pump driveshaft - Replace defective component.
| Trim does not fully up or down |
Defective pump assembly - Change pump.
Tilt ram piston ball is in wrong position - Clean or repair.
Damaged tilt ram piston O-ring - Install new O-ring.
Insufficient oil - Check oil level and add oil as required.
Lower check valve is not properly secured in port side trim ram - Secure valve properly.
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