Yamaha 20DMH Troubleshooting
| Engine Model: Yamaha 20DMH |
| Engine Type: 2-stroke 2-cylinder gasoline outboard engine |
| Total Displacement: 24.1 cu.in (395 cc) |
| Rated Engine Power: 20 Hp (14.7 kW) at 6000 rpm |
| Fuel System: Carburetor |
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| Engine difficult to start or won't start |
Gas tank is empty - Add gasoline.
Low-quality gasoline - Change gasoline.
There is air in the fuel system - Bleed the system.
Loose or disconnected spark plug wire - Check the spark plug wire connection, repair or replace.
Spark plug is damaged - Install new spark plug.
Fuel filter is clogged - Change fuel filter.
Carburetor is not adjusted - Check carburetor float adjustment.
Fuel lines clogging - Service fuel lines.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Fuel pump pressure is low - Install new pump or repair it.
Worn or defective reed valve - Replace reed valve as required.
| Engine starts and stops suddenly |
Spark plug is damaged - Change spark plug as required.
Carburetor is defective or clogged - Replace or service carburetor.
Ignition coil is not working - Ignition coil must be replaced.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Low fuel pump pressure - Change or rebuild fuel pump.
Ignition system is defective - Check ignition and replace faulty components.
Fuel pump is defective or dirty - Clean or change fuel pump.
Carburetor not adjusted - Adjust according to instructions.
Dirt in the fuel lines - Service fuel lines.
Closed or clogged fuel tank air vent - Open or service air vent.
Clogged fuel filter - Install new filter.
Damaged gaskets - Change gaskets.
Engine overload - Reduce engine load.
Carburetor is running lean - Set the carburetor correctly.
Ignition timing is wrong - Set the ignition timing correctly.
Damaged thermostat - Install new thermostat.
Water pump malfunction - Install new water pump.
Propeller pitch or diameter incorrect - Install correct propeller.
Propeller bent or damaged - Replace propeller.
Outboard motor is mounted too high or too low - Position the engine correctly.
| Engine knocking sound or abnormal noise |
Low octane fuel - Change gasoline.
Engine overload - Reduce engine load.
Incorrectly adjusted low idle speed - Correct the settings.
Fuel pump is dirty or defective - Clean or change fuel pump.
Worn main bearings or crankshaft - Have bearings or crankshaft replaced.
Worn cylinder bore or piston rings - Replace defective parts.
Clogged or improperly adjusted carburetor - Clean or properly adjust carburetor.
Clogged or defective fuel pump - Inspect fuel pump and change as required.
Ignition system malfunction - Inspect ignition system and change faulty parts.
Gaskets are damaged - Install new gaskets.
Powerhead parts are damaged - Replace defective parts as required.
Propeller selection improperly - Replace propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Motor mounted at incorrect height on transom - Adjust the outboard motor height correctly.
Incorrect trim angle - Adjust trim angle.
| Excessive fuel consumption |
Improper adjustment of carburetor main jet - Adjust it properly.
Faulty or loose spark plug - Change or re-tighten spark plug.
Rings, sleeve, or piston are damaged - Replace defective parts.
| Motor vibrates excessively |
Damaged or improper size of propeller - Have propeller repaired or replaced.
Damaged propeller shaft - Have propeller shaft replaced.
Weeds clogs the propeller - Remove and clean propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Loose or faulty steering pivot Tighten correctly or replace.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
