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| Home / Outboard Engines / Tohatsu Engines / Tohatsu M3.5B2 |
Tohatsu M3.5B2 Troubleshooting
The Tohatsu M3.5B2 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 manual starting system, dog clutch shift 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 is not starting or hard starting |
Gas tank is empty - Fill it up.
Incorrect fuel grade - Use quality gasoline.
Air or water in fuel system - Remove water or air from fuel system.
Spark plug wiring connection is defective - Check the spark plug wire connection, repair or replace.
Faulty spark plug - Replace spark plug.
Plugged fuel filter - Change fuel filter.
Carburetor incorrectly set - Set carb correctly.
Fuel lines are clogged - Service fuel lines.
Fuel tank air vent clogged or closed - Open or service air vent.
Lack of fuel pump pressure - Replace or repair fuel pump.
Reed valve is faulty or worn - Replace reed valve.
| Engine starts and stops suddenly |
Spark plug is defective - Change spark plug.
Defective or dirty carburetor - Repair or clean carburetor.
Ignition coil is defective - Install a new ignition coil.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Fuel pump pressure is low - Install new fuel pump or rebuild it.
| Rough engine running |
Ignition system problems - Check ignition and replace faulty components.
Clogged or damaged fuel pump - Clean or install new fuel pump.
Carburetor problems - Carburetor diagnostics required.
Fuel lines are clogged - Fuel lines must be clean.
Fuel tank air vent clogged or closed - Fuel tank air vent need to be opened or cleaned.
Fuel filter is plugged - Fuel filter needs changing.
Worn gaskets - Change gaskets.
| Engine overheated |
Engine overloaded - Reduce engine load.
Too lean fuel mixture in carburetor - Use proper settings.
Improper ignition timing - Adjust ignition timing as required.
Thermostat is faulty - Change thermostat.
Water pump is defective - Water pump need to be replaced.
Propeller selection improperly - Replace propeller.
Propeller bent or damaged - Replace propeller.
Outboard motor is positioned too low or too high - Position the engine correctly.
| Abnormal engine noise or knocking |
Stale gasoline - Use proper fuel.
Engine overload - Load reducing is recommended.
Too low idle RPM - Adjust idle speed.
Fuel pump is damaged or dirty - Service or change fuel pump.
Worn crankshaft or main bearings - Repair or replace defective parts.
Cylinder bore or piston rings are damaged - Replace faulty components.
| Low engine power |
Carburetor is incorrectly adjusted or dirty - Clean or correctly adjust carburetor.
Dirty or faulty fuel pump - Clean or replace fuel pump.
Ignition system is defective - Check ignition system and replace faulty parts.
Damaged gaskets - Install new gaskets.
Damaged powerhead parts - Replace defective components.
Propeller selection improperly - Install correct propeller.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard engine mounting height improperly - Adjust the outboard motor height correctly.
Improper trim angle - Make the correct trim angle adjustment.
| Engine uses too much fuel |
Incorrect adjustment of carburetor main jet - Adjust the carburetor main jet correctly.
Loose or faulty spark plug - Spark plug need to be replaced or tightened.
Piston, sleeve, or rings are damaged - Change faulty parts.
| Engine vibrates excessively |
Propeller bent or damaged - Replace propeller.
Propeller shaft malfunction - Propeller shaft needs to be replaced.
Weeds clogs the propeller - Remove weeds from propeller.
Engine mounting bolt is not tightened - Tighten the bolt as required.
Damaged or loose steering pivot Tighten correctly or replace.
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