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| Home / Outboard Engines / Tohatsu Engines / Tohatsu M25C2 |
Tohatsu M25C2 Troubleshooting
The Tohatsu M25C2 is a 2-stroke 2-cylinder forced water-cooled gasoline outboard engine with a rated power of 25 hp (18.4 kW) at 4800-5500 rpm. The engine cylinder bore is 2.68" (68 mm) and piston stroke is 2.32" (59 mm). A 26.2 cubic inches (429 cc) outboard motor has a fuel system with horizontal type carburetor, starting system with manual starter, flywheel magneto capacitor discharge ignition system, dog clutch shift system, manual trim/tilt, and handle tiller steering. The fuel tank capacity is 6.3 gal (24 liters). The propeller is made of aluminum and it has three blades.
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| Engine starts up hard or will not start |
Empty fuel tank - Fill gasoline up.
Wrong grade of gasoline - Use quality gasoline.
Dirty fuel lines - Inspect and clean.
Damaged spark plug wiring connection - Check spark plug wiring connection, repair or change.
Spark plug is defective - Change spark plug.
Fuel filter is dirty - Replace or clean fuel filter.
Carburetor is not adjusted - Check carburetor float adjustment.
Dirty fuel lines - Fuel lines must be clean.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Low fuel pump pressure - Replace or rebuild fuel pump.
Reed valve is faulty or worn - Install new reed valve.
| Engine starts but stops suddenly |
Defective spark plug - Replace spark plug.
Carburetor is dirty or faulty - Carburetor needs to be replaced or cleaned.
Damaged ignition coil - Ignition coil should be replaced.
Fuel tank air vent closed or restricted - Open or clean air vent.
Fuel pump pressure is low - Change or rebuild fuel pump.
| Unstable engine running |
Defective ignition system - Test ignition and replace failed parts.
Dirty or damaged fuel pump - Inspect fuel pump and change as required.
Carburetor malfunction - Check and repair as required.
Clogged fuel lines - Clean fuel lines.
Closed or restricted fuel tank air vent - Open or clean air vent.
Fuel filter is plugged - Replace or clean fuel filter.
Gaskets are defective - Replace gaskets.
| Engine keeps overheating |
Engine overloaded - Reduce engine load.
Too lean carburetor mixture - Adjust carburetor properly.
Ignition timing is improper - Set the ignition timing correctly.
Damaged thermostat - Change thermostat as required.
Water pump is defective - Change water pump.
Incorrect propeller selection - Check the propeller size.
Propeller bent or damaged - Replace propeller.
Outboard motor is mounted too high or too low - Mount the motor as required.
| Engine knocking or noise |
Stale or low octane fuel - Use proper gasoline.
Engine is running overloaded - Reduce the load.
Incorrect low idle setting - Adjust idle speed.
Clogged or damaged fuel pump - Clean or change fuel pump.
Main bearings or crankshaft are worn out - Worn parts replacement required.
Worn piston rings or cylinder bore - Change defective parts.
| Low engine power |
Carburetor is clogged or improperly adjusted - Clean or properly adjust carburetor.
Fuel pump is faulty or clogged - Clean or change fuel pump.
Ignition system failure - Inspect ignition system and change faulty parts.
Gaskets are damaged - Install new gaskets.
Worn powerhead parts - Replace defective parts as required.
Propeller selection improperly - Check the propeller size.
Propeller bent or damaged - Replace propeller.
Motor mounted at incorrect height on transom - Check the outboard motor mounting height.
Trim angle is incorrect - Make the correct trim angle adjustment.
| Engine uses too much fuel |
Carburetor main jet adjustment is improper - Adjust it correctly.
Faulty or loose spark plug - Re-tighten or replace spark plug.
Piston, sleeve, or rings are damaged - Replace faulty components.
| Excessive motor vibration |
Propeller bent or damaged - Have propeller repaired or replaced.
Propeller shaft malfunction - Have propeller shaft replaced.
Weeds clogs the propeller - Clean the 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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