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Tohatsu MFS6CD Troubleshooting
The Tohatsu MFS6CD is a four-stroke single-cylinder OHV shallow water drive gasoline outboard engine. This engine has a carburetor fuel system, mechanical fuel pump, water cooled with thermostat, and flywheel magneto CDI ignition system. A 7.5 cu.in (123 cc) outboard motor has a cylinder bore of 2.32" (59 mm), piston stroke of 1.77" (45 mm), and max power of 6 hp (4.4 kW) at 5000-6000 rpm. The boat motor is equipped with a dog clutch shift system, manual starting system, 3-blades aluminum standard propeller, manual trim and tilt, and tiller handle or remote control steering system. The bult-in fuel tank has a capacity of 0.3 gal (1.15 liters).
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| Engine won't start or starts hard |
Fuel tank is empty - Fill it up.
Improper fuel grade - Use quality fuel.
Dirt and debris in fuel system - Remove debris and dirt.
Damaged spark plug wiring connection - Inspect spark plug wiring connection, change or repair.
Faulty spark plug - Install new spark plug.
Fuel filter is dirty - Fuel filter needs changing.
Carburetor problems - Carburetor diagnostics required.
Dirt in the fuel lines - Fuel lines need to be cleaned.
Closed or restricted 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 - Adjust properly or change the cable.
Valve clearance is improper - Check and adjust.
Wrong valve timing - Adjust valve timing as required.
| Engine starts but then stops |
Defective spark plug - Install new spark plug.
Carburetor is clogged or faulty - Clean or change carburetor.
Ignition coil is faulty - Replace ignition coil as necessary.
Fuel tank air vent closed or restricted - Fuel tank air vent need to be opened or cleaned.
Fuel pump malfunction - Replace or rebuild fuel pump.
Faulty choke system - Inspect and replace choke system components.
Incorrect valve clearance - Need to adjust valve clearance.
Valve timing is improper - Adjust valve timing as required.
Valve springs are broken or bad - Install new valve springs.
Valves sticking - Valves need to be cleaned.
| Engine runs roughly |
Ignition system malfunction - Check ignition and replace faulty components.
Fuel pump is damaged or dirty - Inspect fuel pump and change as required.
Carburetor problems - Carburetor diagnostics required.
Fuel lines clogging - Fuel lines must be clean.
Closed or clogged fuel tank air vent - Open or clean air vent.
Fuel filter is plugged - Install new filter.
Gaskets are defective - Change gaskets.
Water intake screen is dirty - Need to wash or clean.
Damaged choke system - Inspect and replace choke system components.
| Engine overheats |
Engine is under excessive load - Load reducing required.
Carburetor is running lean - Adjust carburetor correctly.
Incorrect ignition timing - Set the ignition timing properly.
Damaged thermostat - Change thermostat as required.
Water pump malfunction - Change water pump as required.
Propeller pitch or diameter incorrect - Replace propeller.
Damaged or improper size of propeller - Replace propeller.
Outboard motor is mounted too high or too low - Position the engine correctly.
Engine oil level is insufficient - Need to add engine oil.
Oil pump malfunction - Install new oil pump.
Water intake is clogged - Wash or clean as required.
Valve setting is improper - Adjust valves correctly.
| Engine knocks or noises |
Stale fuel - Use correct gasoline.
Engine overload - Load reducing required.
Incorrect low idle setting - Test and adjust.
Clogged or damaged fuel pump - Service or replace fuel pump.
Crankshaft or main bearings failure - Worn parts replacement required.
Damaged piston rings or cylinder bore - Replace defective components.
| Low engine power |
Clogged or incorrectly adjusted carburetor - Clean or properly adjust carburetor.
Fuel pump is damaged or dirty - Test fuel pump and change if necessary.
Defective ignition - Inspect ignition system and change failed components.
Cylinder head gasket is damaged - Replace the head gasket.
Powerhead parts are faulty - Defective components need to be replaced.
Valves are burned or stuck - Replace or clean valves.
Propeller selection improperly - Install correct propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard engine mounting height improperly - Adjust the engine to correct transom height.
Incorrect trim angle - Adjust trim angle correctly.
| Excessive fuel consumption |
Improper carburetor main jet adjustment - Adjust main jet as required.
Loose or faulty spark plug - Change or re-tighten spark plug.
Sleeve, rings, or piston are damaged - Replace defective components as required.
| Engine vibrates excessively |
Damaged or improper size of propeller - Have propeller repaired or replaced.
Propeller shaft damaged - Replace propeller shaft.
Weeds in the propeller - Clean the propeller.
Engine mounting bolt is not tightened - Tighten bolt.
Steering pivot is loose or damaged Tighten correctly or replace.
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