Yamaha 25MLH Troubleshooting
| Engine Model: Yamaha 25MLH |
| Engine Type: 2-stroke 2-cylinder long shaft gasoline outboard engine |
| Total Displacement: 24.1 cu.in (395 cc) |
| Rated Engine Power: 25 Hp (18.4 kW) at 6000 rpm |
| Fuel System: Carburetor |
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| Engine difficult to start or will not start |
No gasoline in tank - Add gasoline.
Wrong grade of gasoline - Use quality gasoline.
Air in the fuel pipes - Bleed the fuel pipes.
Loose or disconnected spark plug wire - Inspect the spark plug wire connection, replace or repair.
Defective spark plug - Change spark plug as required.
Plugged fuel filter - Replace or clean fuel filter.
Carburetor components worn out - Repair or replace parts.
Dirt in the fuel lines - Clean fuel system lines.
Closed or restricted fuel tank air vent - Open or service air vent.
Low fuel pump pressure - Change or rebuild fuel pump.
Damaged or worn fuel reed valve - Replace reed valve as required.
| Engine stops after starting |
Defective spark plug - Change spark plug.
Defective or dirty carburetor - Service or repair carburetor.
Defective ignition coil - Replace ignition coil as necessary.
Fuel tank air vent restricted or closed - Open or clean air vent.
Lack of fuel pump pressure - Replace or rebuild fuel pump.
Ignition system is defective - Inspect ignition system and change faulty parts.
Dirty or defective fuel pump - Check fuel pump and replace if necessary.
Carburetor is dirty - Wash, clean and adjust.
Restricted fuel lines - Service fuel lines.
Closed or restricted fuel tank air vent - Open or clean air vent.
Fuel filter is dirty - Fuel filter needs changing.
Gaskets are defective - Replace gaskets.
Engine is under excessive load - Reduce load.
Carburetor is running lean - Set the carburetor correctly.
Ignition timing is incorrect - Set the ignition timing correctly.
Faulty thermostat - Thermostat need to be replaced.
Water pump failure - Replace water pump.
Propeller pitch or diameter incorrect - Check the propeller size.
Propeller bent or damaged - Replace propeller.
Outboard engine is positioned too low or too high - Mount the motor as required.
Low octane gasoline - Use proper fuel.
Engine overloaded - Load reducing is recommended.
Incorrect low idle setting - Adjust as required.
Fuel pump is defective or dirty - Test fuel pump and replace if necessary.
Crankshaft or main bearings wear - Replace crankshaft or bearings.
Piston rings or cylinder bore are worn - Change defective components.
Clogged or incorrectly adjusted carburetor - Carburetor needs to be adjusted correctly or cleaned.
Dirty or faulty fuel pump - Test fuel pump and replace if necessary.
Defective ignition system - Inspect ignition system and change faulty parts.
Worn gaskets - Install new gaskets.
Faulty powerhead components - Replace defective parts.
Incorrect propeller selection - Check the propeller size.
Damaged or improper size of propeller - Replace propeller.
Motor mounted at incorrect height on transom - Check the outboard engine mounting height.
Trim angle is incorrect - Adjust trim angle.
| Excessive fuel consumption |
Incorrect carburetor main jet adjustment - Adjust it properly.
Spark plug is defective or loose - Tighten or replace spark plug.
Worn sleeve, piston, or rings - Change faulty components.
| Excessive motor vibration |
Damaged or improper size of propeller - Have propeller repaired or replaced.
Propeller shaft malfunction - Replace propeller shaft.
Weeds wraped around propeller - Clean the propeller.
Engine mounting bolt is not tightened - Tighten bolt.
Loose or faulty steering pivot Tighten or replace.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
