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| Home / Outboard Engines / Tohatsu Engines / Tohatsu M4C |
Tohatsu M4C Troubleshooting
The Tohatsu M4C is a 2-stroke 1-cylinder forced water-cooled gasoline outboard engine with a rated power of 4 hp (2.9 kW) at 4500-5500 rpm. The engine cylinder bore is 2.17" (55 mm) and piston stroke is 1.69" (43 mm). A 6.2 cubic inches (102 cc) outboard motor has a carburetor fuel system, dog clutch shift system, starting system with manual starter, flywheel magneto capacitor discharge ignition system, manual tilt, and handle tiller or remote control steering. The fuel tank capacity is 0.65 gal (2.5 liters). The propeller is made of aluminum and it has three blades.
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| Engine starts up hard or will not start |
Fuel tank is empty - Fill it up.
Wrong fuel grade - Change gasoline.
Fuel system clogged - Repair or replace.
Defective spark plug wire connection - Check the spark plug wire connection, repair or replace.
Defective spark plug - Spark plug need to be replaced.
Dirty fuel filter - Change fuel filter.
Carburetor not adjusted - Adjust according to instructions.
Clogged fuel lines - Fuel lines need to be cleaned.
Fuel tank air vent clogged or closed - Open or clean air vent.
Lack of fuel pump pressure - Change or rebuild fuel pump.
Reed valve is faulty or worn - Replace reed valve as required.
| Engine starts but then stops |
Faulty spark plug - Change spark plug.
Carburetor is defective or clogged - Service or repair carburetor.
Ignition coil is defective - Change ignition coil as required.
Fuel tank air vent clogged or closed - Open or service air vent.
Fuel pump pressure is low - Replace or rebuild fuel pump.
| Engine runs roughly |
Ignition failure - Test ignition and replace failed parts.
Fuel pump is dirty or defective - Test fuel pump and replace if necessary.
Carburetor problems - Carburetor diagnostics required.
Dirty fuel lines - Clean fuel system lines.
Closed or restricted fuel tank air vent - Open or service air vent.
Fuel filter is dirty - Fuel filter needs to be replaced.
Gaskets are worn - Change gaskets.
| Engine overheated |
Engine overloaded - Load reducing is recommended.
Too lean fuel mixture in carburetor - Set the carburetor properly.
Ignition timing is improper - Ignition timing needs to be adjusted correctly.
Damaged thermostat - Change thermostat.
Water pump is defective - Water pump need to be replaced.
Incorrect propeller selection - Replace propeller.
Damaged or bent propeller - Replace propeller.
Outboard engine is positioned too low or too high - Position the engine correctly.
| Engine noise or knocking |
Stale or low octane fuel - Change fuel.
Excessive engine load - Load reducing required.
Wrong adjustment of low idle speed - Adjust idling as required.
Dirty or damaged fuel pump - Test fuel pump and change if necessary.
Main bearings or crankshaft are worn out - Worn parts replacement required.
Damaged cylinder bore or piston rings - Change faulty parts.
| Engine power is too low |
Carburetor is dirty or incorrectly adjusted - Service or correctly adjust carburetor.
Fuel pump is dirty or defective - Test fuel pump and replace if necessary.
Defective ignition system - Check ignition system and replace faulty parts.
Damaged gaskets - Install new gaskets.
Powerhead parts are faulty - Defective components need to be replaced.
Improper propeller diameter or pitch - Install correct propeller.
Damaged or bent propeller - Replace propeller.
Incorrect outboard motor mounting height - Check the outboard motor mounting height.
Incorrect trim angle - Adjust trim angle.
| High fuel consumption |
Carburetor main jet is incorrectly adjusted - Adjust the carburetor main jet properly.
Loose or faulty spark plug - Tighten or change the spark plug.
Worn piston, rings, or sleeve - Replace faulty parts.
| Excessive motor vibration |
Propeller bent or damaged - Have propeller repaired or replaced.
Propeller shaft malfunction - Replace propeller shaft.
Weeds wraped around propeller - Remove and clean propeller.
Engine mounting bolt is not tightened - Tighten the bolt as required.
Steering pivot is loose or damaged Tighten or replace.
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