Yamaha 25DM Troubleshooting
| Engine Model: Yamaha 25DM |
| Engine Type: 2-stroke 2-cylinder gasoline outboard engine |
| Total Displacement: 26.2 cu.in (430 cc) |
| Rated Engine Power: 25 Hp (18.4 kW) at 5500 rpm |
| Fuel System: Carburetor |
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| Engine hard to start or will not start |
Gas tank is empty - Fill gasoline up.
Improper fuel grade - Use quality gasoline.
Air or water in fuel system - Remove water or air from fuel system.
Defective spark plug wire connection - Check spark plug wiring connection, repair or change.
Spark plug is defective - Replace spark plug.
Dirty fuel filter - Fuel filter needs changing.
Carburetor is not adjusted - Check carburetor float adjustment.
Fuel lines clogging - Service fuel lines.
Fuel tank air vent restricted or closed - Open or clean air vent.
Low fuel pump pressure - Replace or rebuild fuel pump.
Reed valve is worn or damaged - Replace reed valve.
| Engine starts and immediately shuts off |
Damaged spark plug - Replace spark plug.
Carburetor is dirty or defective - Service or replace carburetor.
Defective ignition coil - Install a new ignition coil.
Fuel tank air vent closed or restricted - Open or service air vent.
Lack of fuel pump pressure - Install new pump or repair it.
Ignition system malfunction - Inspect ignition system and change failed components.
Clogged or damaged fuel pump - Clean or change fuel pump.
Carburetor malfunction - Check and repair as required.
Dirty fuel lines - Clean fuel lines.
Fuel tank air vent restricted or closed - Open or service air vent.
Fuel filter is clogged - Install new filter.
Damaged gaskets - Replace gaskets.
Engine is running overloaded - Load reducing is recommended.
Carburetor fuel mixture is too lean - Set the carburetor correctly.
Incorrect ignition timing - Set the ignition timing properly.
Defective thermostat - Change thermostat as required.
Damaged water pump - Change water pump.
Improper propeller diameter or pitch - Check the propeller size.
Damaged or improper size of propeller - Replace propeller.
Outboard engine is mounted too high or too low - Position the engine correctly.
| Abnormal engine knocking or noise |
Low octane fuel - Use proper gasoline.
Engine is overloaded - Load reducing is recommended.
Incorrectly adjusted low idle speed - Adjust idling as required.
Clogged or defective fuel pump - Clean or install new fuel pump.
Worn crankshaft or main bearings - Install new parts as as required.
Damaged piston rings or cylinder bore - Change faulty components.
Improperly adjusted or dirty carburetor - Adjust the carburetor correctly or clean it.
Dirty or faulty fuel pump - Service or replace fuel pump.
Ignition system malfunction - Inspect ignition system and change failed components.
Gaskets are defective - Change gaskets.
Damaged powerhead parts - Replace defective parts as required.
Incorrect propeller selection - Replace propeller.
Damaged or improper size of propeller - Replace propeller.
Motor mounted at incorrect height on transom - Adjust the outboard motor height correctly.
Improper trim angle - Adjust trim angle.
| Excessive fuel consumption |
Improper carburetor main jet adjustment - Adjust the carburetor main jet correctly.
Spark plug is loose or defective - Replace or tighten spark plug.
Rings, sleeve, or piston are damaged - Change defective components.
| Excessive motor vibration |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft damaged - Replace propeller shaft.
Weeds wraped around propeller - Remove weeds from propeller.
Motor mounting bolt is loose - Tighten bolt.
Steering pivot is loose or damaged Tighten correctly or replace.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
