Tohatsu MFS15C Troubleshooting
| Engine Model: Tohatsu MFS15C |
| Engine Type: 4-stroke 2-cylinder SOHC gasoline outboard engine |
| Total Displacement: 21.4 cu.in (351 cc) |
| Rated Engine Power: 15 Hp (11 kW) at 5500 rpm |
| Fuel System: Fuel Injection |
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| Engine starts hard or won't start |
Gas tank is empty - Fill gasoline up.
Low-quality gasoline - Change gasoline.
Air in fuel system - Bleed fuel system.
Spark plug wire connection are damaged - Check the spark plug wire connection, repair or replace.
Faulty spark plug - Spark plug need to be replaced.
Plugged fuel filter - Replace fuel filter.
Worn or damaged vapor separator needle valve - Change vapor separator needle valve.
Dirt in the fuel lines - Fuel lines need to be cleaned.
Fuel tank air vent closed or restricted - Fuel tank air vent need to be opened or cleaned.
Defective fuel feed pump - Replace or rebuild fuel feed pump.
Improperly adjusted or worn throttle cable - Replace cable or adjust properly.
Valve clearance is not correct - Adjust valve clearance according to specifications.
Valve timing is improper - Set the valve timing correctly.
Fuel pressure is low - Inspect low pressure fuel pump or inspect fuel system for leaks.
Fuel injector is damaged or dirty - Clean or install new injector.
Fuel regulator failure - Install new fuel regulator.
ECM failure - Replace ECM.
| Engine starts and stops immediately |
Damaged spark plug - Spark plug need to be replaced.
Vapor separator needle valve is worn or defective - Replace needle valve.
Ignition coil is damaged - Change ignition coil as required.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Faulty fuel pump - Replace or rebuild fuel pump.
Choke system is damaged - Check and repair choke system.
Improper valve clearance - Adjust valve clearance.
Valve timing is wrong - Adjust valve timing correctly.
Damaged or weak valve springs - New valve springs need to be installed.
Valves are stuck - Valves need to be cleaned.
Low cylinder compression - Inspect and replace defective parts.
Dirty fuel filter - Fuel filter needs to be replaced.
Fuel injector is damaged or dirty - Clean or install new injector.
Engine oil level is insufficient - Check and refill engine oil.
Faulty oil pump - Oil pump need to be replaced.
Clogged water intake - Need to wash or clean.
Thermostat is faulty - Replace thermostat.
Damaged water pump - Water pump need to be replaced.
Ignition failure - Inspect ignition system and change failed components.
Clogged or defective fuel pump - Clean or replace fuel pump.
Worn or damaged vapor separator needle valve - Change vapor separator needle valve.
Fuel lines are dirty - Clean fuel lines.
Fuel tank air vent closed or restricted - Fuel tank air vent need to be opened or cleaned.
Plugged fuel filter - Replace fuel filter.
Intake manifold is air leaking - Replace intake manifold gasket.
Clogged water intake - Need to wash or clean.
Throttle link and throttle valve are worn or damaged - Replace faulty parts.
Fuel injector is dirty or worn - Clean or replace as required.
Engine is under excessive load - Reduce engine load.
Clogged fuel pump or fuel injector - Replace or clean if necessary.
Improper ignition timing - Set the ignition timing correctly.
Thermostat is defective - Change thermostat.
Water pump is defective - Replace water pump.
Incorrect propeller selection - Replace propeller.
Damaged or bent propeller - Replace propeller.
Outboard motor is mounted too high or too low - Mount the motor as required.
Engine oil insufficient - Fill the crankcase with engine oil.
Damaged oil pump - Install new oil pump.
Water intake is clogged - Wash or clean as required.
Improper valve setting - Adjust valves as required.
Stale or low octane fuel - Use proper gasoline.
Engine overloaded - Load reducing required.
Improperly adjusted low idle speed - Adjustment required.
Fuel pump is clogged or faulty - Test fuel pump and replace if necessary.
Main bearings or crankshaft wear - Need to install new components.
Cylinder bore or piston rings are worn - Replace defective parts.
Fuel lines clogging - Fuel lines need to be cleaned.
Damaged fuel injector - Inspect fuel injector and change as required.
Clogged or damaged fuel pump - Check fuel pump and change if required.
Ignition failure - Inspect ignition system and change failed components.
Damaged cylinder head gasket - Change cylinder head gasket.
Worn powerhead components - Replace defective components.
Valves are stuck or burned - Service or replace valves.
Improper propeller diameter or pitch - Check the propeller size.
Damaged or bent propeller - Have propeller repaired or replaced.
Engine mounted at wrong transom height - Check the outboard engine mounting height.
Trim angle is incorrect - Make the correct trim angle adjustment.
| Engine using too much gasoline |
Fuel injector is dirty or worn - Clean or replace as required.
Defective or loose spark plug - Replace or tighten spark plug.
Worn piston, rings, or sleeve - Change faulty components.
ECU is not functioning - Replace ECU.
| Excessive motor vibration |
Propeller bent or damaged - Replace propeller.
Propeller shaft damaged - Have propeller shaft replaced.
Weeds in the propeller - Remove and clean propeller.
Engine mounting bolt is not tightened - Tighten the bolt as required.
Loose or faulty steering pivot Tighten or replace.
Battery power is low - Low battery charging, charge as required.
Battery runs out quickly - Service charging system or install new battery.
Bad terminals or disconnected battery cables - Check wire connections and change or service terminals.
Starter motor is defective - Repair or install a new starter.
| Trim motor runs but trim system does not move up or down |
Oil level is insufficient - Fill up oil to required level.
Pump assembly faulty - Inspect pump and change as required.
Leakage of manual drain valve - Valve need to be closed or changed.
Pump driveshaft or motor damaged - Change defective component.
| Trim cannot be fully up or down |
Pump assembly is defective - Change pump.
Tilt ram piston ball is displaced - Clean or repair.
Worn tilt ram piston O-ring - Change O-ring.
Low oil level - Check and refill oil.
Lower check valve is not properly secured in port side trim ram - Secure valve properly.
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