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Tohatsu M3.5A2 Troubleshooting
The Tohatsu M3.5A2 is a two-stroke single-cylinder gasoline outboard engine. This engine has a carburetor fuel system, forced water cooling, and flywheel magneto CDI ignition system. A 4.6 cu.in (74.5 cc) outboard motor has a cylinder bore of 1.85" (47 mm), piston stroke of 1.69" (43 mm), and maximum power of 3.5 hp (2.6 kW) at 4200-5300 rpm. The boat motor is equipped with a forward-neutral gear shift, manual starting system, 3-blades aluminum standard propeller, manual trim and tilt, and tiller handle steering system. The fuel tank has a capacity of 0.35 gal (1.4 liters).
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| Engine starts up hard or won't start |
Gas tank is empty - Fill gasoline up.
Wrong grade of gasoline - Use correct gasoline grade.
Fuel system clogged - Repair or replace.
Disconnected or loose spark plug wire - Check spark plug wiring connection, repair or change.
Faulty spark plug - Spark plug need to be replaced.
Clogged fuel filter - Replace fuel filter.
Carburetor malfunction - Check and repair as required.
Fuel lines clogging - Fuel lines need to be cleaned.
Fuel tank air vent closed or restricted - Fuel tank air vent need to be opened or cleaned.
Fuel pump pressure is low - Install new pump or repair it.
Reed valve is worn or damaged - Replace reed valve as required.
| Engine starts and then shuts off |
Spark plug is damaged - Spark plug need to be replaced.
Carburetor is clogged or defective - Replace or service carburetor.
Ignition coil is faulty - Install a new ignition coil.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Low fuel pump pressure - Replace or repair fuel pump.
| Engine runs irregularly |
Ignition system problems - Test ignition and replace failed parts.
Fuel pump is dirty or defective - Clean or install new fuel pump.
Carburetor is not adjusted - Check carburetor float adjustment.
Clogged fuel lines - Clean fuel system lines.
Fuel tank air vent restricted or closed - Fuel tank air vent need to be opened or cleaned.
Fuel filter is plugged - Replace or clean fuel filter.
Gaskets are defective - Change gaskets.
| Engine overheats |
Engine overloaded - Load reducing required.
Carburetor fuel mixture is too lean - Set the carburetor correctly.
Improper ignition timing - Set the ignition timing correctly.
Faulty thermostat - Install new thermostat.
Water pump malfunction - Water pump need to be replaced.
Propeller selection improperly - Install correct propeller.
Damaged or improper size of propeller - Have propeller repaired or replaced.
Outboard engine is positioned too low or too high - Mount the motor as required.
| Engine knocking or noise |
Low octane fuel - Change fuel.
Engine is under excessive load - Reduce load.
Incorrectly adjusted low idle speed - Adjust idle speed.
Fuel pump is damaged or dirty - Test fuel pump and replace if necessary.
Crankshaft or main bearings are worn out - Install new parts as as required.
Piston rings or cylinder bore are worn - Replace faulty components.
| Lack of engine power |
Carburetor is clogged or incorrectly adjusted - Service or correctly adjust carburetor.
Clogged or damaged fuel pump - Check fuel pump and replace if necessary.
Ignition failure - Test ignition and replace failed parts.
Worn gaskets - Change gaskets.
Worn powerhead parts - Replace defective parts as required.
Incorrect propeller selection - Check the propeller size.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard motor mounting height is set incorrectly - Check the outboard motor mounting height.
Incorrect trim angle - Adjust trim angle.
| Excessive fuel consumption |
Carburetor main jet is improperly adjusted - Adjust the carburetor main jet correctly.
Spark plug is loose or defective - Re-tighten or replace spark plug.
Sleeve, rings, or piston are damaged - Replace defective parts as required.
| Excessive engine vibration |
Propeller bent or damaged - Replace propeller.
Damaged propeller shaft - Have propeller shaft replaced.
Weeds wraped around propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten bolt.
Steering pivot is loose or damaged Tighten or replace.
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