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Tohatsu M6B Troubleshooting
The Tohatsu M6B is a two-stroke two-cylinder gasoline outboard engine. This engine has a carburetor fuel system, thermostatically controlled cooling system, and flywheel magneto CDI ignition system. A 10.3 cu.in (169 cc) outboard motor has a cylinder bore of 1.97" (50 mm), piston stroke of 1.69" (43 mm), and maximum power of 6 hp (4.4 kW) at 4500-5500 rpm. The boat motor is equipped with a forward-neutral-reverse gear shift, manual starting system, 3-blades aluminum standard propeller, manual trim and tilt, and tiller handle or remote control steering system. The fuel tank has a capacity of 3.2 gal (12 liters).
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| Engine starts up hard or won't start |
No fuel in fuel tank - Add fuel.
Wrong grade of gasoline - Change fuel.
Air in the fuel pipes - Bleed the fuel pipes.
Spark plug wire is disconnected or loose - Inspect the spark plug wire connection, replace or repair.
Damaged spark plug - Replace spark plug.
Plugged fuel filter - Fuel filter needs changing.
Incorrect carburetor adjustment - Adjust carburetor idle mixture screw.
Dirty fuel lines - Clean fuel lines.
Fuel tank air vent clogged or closed - Open or clean air vent.
Lack of fuel pump pressure - Repair or change fuel pump.
Reed valve is defective or worn - Replace reed valve as required.
| Engine starts but then stops |
Spark plug is defective - Install new spark plug.
Carburetor is dirty or faulty - Service or change carburetor.
Ignition coil is faulty - Ignition coil should be replaced.
Closed or restricted fuel tank air vent - Open or service air vent.
Lack of fuel pump pressure - Repair or change fuel pump.
| Engine runs intermittently |
Ignition system problems - Check ignition system and replace faulty parts.
Dirty or defective fuel pump - Inspect fuel pump and change as required.
Problems with carburetor adjustment - Adjust as required.
Clogged fuel lines - Service fuel lines.
Closed or restricted fuel tank air vent - Open or service air vent.
Dirty fuel filter - Change fuel filter.
Worn gaskets - Replace gaskets.
| Engine is overheated |
Engine overloaded - Reduce engine load.
Carburetor fuel mixture is too lean - Set the carburetor correctly.
Ignition timing is improper - Ignition timing needs to be set properly.
Faulty thermostat - Thermostat need to be replaced.
Damaged water pump - Replace water pump.
Improper propeller diameter or pitch - Check the propeller size.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard engine is mounted too high or too low - Position the engine correctly.
| Engine noise or knocking |
Low octane fuel - Use proper gasoline.
Engine overloaded - Load reducing is recommended.
Incorrect low idle setting - Correct idle adjustment.
Fuel pump is dirty or defective - Service or replace fuel pump.
Worn main bearings or crankshaft - Worn parts replacement required.
Cylinder bore or piston rings are worn - Change faulty parts.
| Lack of engine power |
Carburetor is dirty or incorrectly adjusted - Adjust the carburetor properly or clean it.
Fuel pump is dirty or defective - Clean or replace fuel pump.
Ignition system problems - Inspect ignition system and change failed components.
Damaged gaskets - Change gaskets.
Powerhead parts are damaged - Replace defective parts as required.
Propeller pitch or diameter incorrect - Replace propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard engine mounting height improperly - Check the outboard engine mounting height.
Incorrect trim angle - Adjust trim angle correctly.
| Engine using too much gasoline |
Improper carburetor main jet adjustment - Adjust the carburetor main jet properly.
Faulty or loose spark plug - Tighten or replace spark plug.
Worn piston, rings, or sleeve - Replace faulty parts.
| Motor vibrates excessively |
Damaged or bent propeller - Replace propeller.
Damaged propeller shaft - Replace propeller shaft.
Weeds clogs the propeller - Clean the propeller.
Engine mounting bolt is not tightened - Tighten the bolt as required.
Damaged or loose steering pivot Tighten or replace.
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