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Tohatsu MD40B2 Troubleshooting
The Tohatsu MD40B2 is a 2-stroke 3-cylinder TLDI forced water-cooled gasoline outboard engine with a rated power of 40 hp (29.5 kW) at 5150-5850 rpm. The engine cylinder bore is 2.68" (68 mm) and piston stroke is 2.52" (64 mm). A 42.5 cubic inches (697 cc) outboard motor has a two stroke low pressure direct injection fuel system, starting system with electric starter, inductive ignition system, dog clutch shift system, power trim/tilt, and handle tiller or remote control steering. The fuel tank capacity is 6.6 gal (25 liters). The propeller is made of aluminum and it has three blades.
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| Engine difficult to start or won't start |
No gasoline in tank - Fill gasoline up.
Wrong fuel grade - Change gasoline.
Clogged fuel system - Remove clogging.
Disconnected or loose spark plug wire - Inspect spark plug wiring connection, change or repair.
Spark plug is faulty - Replace spark plug.
Clogged fuel filter - Change fuel filter.
Dirty fuel lines - Fuel lines must be clean.
Fuel pressure is low - Check system for fuel leaks or check low pressure fuel pump.
Low air pressure - Normalize air pressure.
Wiring harness connections are damaged - Inspect harness connections.
Damaged ignition system - Check ignition components and replace if necessary.
Fuel feed pump is faulty - Install new fuel feed pump.
Fuel injector is clogged or malfunction - Clean or install new injector.
ECM is not functioning - Install new ECM.
Reed valve is faulty or worn - Replace reed valve as required.
| Engine starts and then stalls |
Spark plug is faulty - Install new spark plug.
Defective ignition coil - Install a new ignition coil.
Damaged fuel pump - Replace fuel pump.
Fuel system is clogged - Clean fuel system.
Fuel filter is dirty - Replace or clean filter.
| Rough engine running |
Defective ignition system - Check ignition and replace faulty components.
Spark plug is defective - Change spark plug.
Clogged or damaged fuel pump - Clean or replace fuel pump.
Air pressure is low - Normalize air pressure.
Restricted fuel lines - Fuel lines must be clean.
Dirty fuel filter - Replace fuel filter.
Direct injector is faulty - Install new injector.
| Engine is overheated |
Engine is overloaded - Load reducing required.
Incorrect ignition timing - Set the ignition timing properly.
Thermostat failure - Install new thermostat.
Defective water pump - Water pump need to be replaced.
Improper propeller diameter or pitch - Check the propeller size.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard motor is positioned too low or too high - Mount the motor as required.
| Abnormal engine noise or knocking |
Low octane fuel - Use correct fuel.
Engine is overloaded - Load reducing required.
Low idle speed setting is not correct - Correct idle settings.
Fuel pump is faulty or clogged - Test fuel pump and replace if necessary.
Main bearings or crankshaft wear - Replace crankshaft or bearings.
Worn cylinder bore or piston rings - Replace faulty components.
| Engine power is insufficient |
Clogged or damaged fuel pump - Test fuel pump and change if necessary.
Ignition system is defective - Inspect ignition system and change failed components.
Worn powerhead components - Change defective components.
Low fuel pressure - Check low pressure fuel pump or check system for fuel leaks.
Low air pressure - Normalize air pressure.
Low compression - Normalize compression.
Fuel delivery problem - Check fuel system.
Fuel regulator is leaking - Leak must be repaired.
Fuel filter is dirty - Change fuel filter.
Dirty or faulty fuel injector - Replace or clean as required.
Manifold fuel leak - Leak must be repaired.
Propeller pitch or diameter incorrect - Check the propeller size.
Damaged or improper size of propeller - Replace propeller.
Incorrect outboard motor mounting height - Have motor adjusted to proper transom height.
Improper trim angle - Adjust trim angle correctly.
| Excessive fuel consumption |
Defective or loose spark plug - Tighten or replace spark plug.
Sleeve, piston, or rings are damaged - Replace defective components.
Engine overloaded - Reduce the load.
Fuel injectors are faulty or clogged - Service or change fuel injectors.
| Engine vibrates excessively |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft damaged - Replace propeller shaft.
Weeds in the propeller - Remove weeds from propeller.
Motor mounting bolt is loose - Tighten bolt.
Loose or faulty steering pivot - Tighten or replace.
| Starter will not work |
Propeller bent or damaged - Replace propeller.
Damaged propeller shaft - Replace propeller shaft.
Weeds wraped around propeller - Remove and clean propeller.
Engine mounting bolt is not tightened - Tighten the bolt as required.
| Trim motor is running but trim system cannot move up or down |
Oil level low - Need to add the oil.
Defective pump assembly - Inspect pump and change as required.
Manual shut-off valve leaks - Close the valve fully or replace it.
Faulty pump driveshaft or motor - Change defective component.
| Trim cannot be fully up or down |
Defective pump assembly - Change pump as required.
Tilt ram piston ball is not positioned correctly - Service or repair.
Worn tilt ram piston O-ring - Change O-ring.
Oil level is low - Fill up oil.
Lower check valve not seating in port side trim ram - Install valve correctly.
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