Mercury 25 2-stroke Troubleshooting
| Engine Model: Mercury 25 Hp |
| Engine Type: 2-stroke 2-cylinder gasoline outboard engine |
| Total Displacement: 24.4 cu.in (400 cc) |
| Rated Engine Power: 25 Hp (18.7 kW) at 6000 rpm |
| Fuel System: Float type carburetor |
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| Engine doesn't start or difficult to start |
No fuel in fuel tank - Add fuel.
Wrong fuel grade - Use quality fuel.
Dirt and debris in fuel system - Remove debris and dirt.
Faulty spark plug wire connection - Check the spark plug wire connection, repair or replace.
Spark plug is faulty - Spark plug need to be replaced.
Plugged fuel filter - Fuel filter needs changing.
Carburetor is not working properly - Inspect and adjust.
Dirt in the fuel lines - Clean fuel lines.
Closed or restricted fuel tank air vent - Open or service air vent.
Fuel pump pressure is low - Change or rebuild fuel pump.
Reed valve is defective or worn - Install new reed valve.
| Engine starts and stops immediately |
Damaged spark plug - Spark plug need to be replaced.
Defective or dirty carburetor - Replace or service carburetor.
Faulty ignition coil - Replace ignition coil as necessary.
Closed or restricted fuel tank air vent - Open or clean air vent.
Fuel pump pressure is low - Install new fuel pump or rebuild it.
| Engine runs intermittently |
Ignition system failure - Check ignition system and replace faulty parts.
Dirty or defective fuel pump - Clean or replace fuel pump.
Incorrect carburetor adjustment - Adjust carburetor idle mixture screw.
Dirt in the fuel lines - Service fuel lines.
Fuel tank air vent closed or restricted - Open or service air vent.
Fuel filter is dirty - Change fuel filter.
Damaged gaskets - Change gaskets.
Engine is running overloaded - Load reducing required.
Carburetor is running lean - Adjust carburetor correctly.
Wrong ignition timing - Set the ignition timing properly.
Thermostat failure - Change thermostat.
Defective water pump - Change water pump as required.
Propeller selection improperly - Replace propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard engine is mounted too high or too low - Mount the motor as required.
Stale gasoline - Use proper gasoline.
Engine is overloaded - Reduce the load.
Incorrect low idle setting - Adjust the low idle speed.
Clogged or defective fuel pump - Clean or install new fuel pump.
Crankshaft or main bearings wear - Install new parts as as required.
Worn cylinder bore or piston rings - Change faulty parts.
| Engine power is insufficient |
Improperly adjusted or dirty carburetor - Service or correctly adjust carburetor.
Dirty or defective fuel pump - Check fuel pump and replace if necessary.
Ignition failure - Check ignition system and replace faulty parts.
Gaskets are worn - Replace gaskets.
Powerhead parts are worn out - Defective components need to be replaced.
Incorrect propeller selection - Replace propeller.
Damaged or improper size of propeller - Have propeller repaired or replaced.
Outboard engine mounting height improperly - Have motor adjusted to proper transom height.
Incorrect trim angle - Adjust trim angle correctly.
Carburetor main jet is incorrectly adjusted - Adjust it properly.
Faulty or loose spark plug - Re-tighten or replace spark plug.
Sleeve, piston, or rings are damaged - Change faulty parts.
| Excessive engine vibration |
Damaged or improper size of propeller - Have propeller repaired or replaced.
Propeller shaft damaged - Propeller shaft needs to be replaced.
Weeds clogs the propeller - Remove and clean propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Damaged or loose steering pivot Tighten or replace.
Low battery voltage - Low battery charging, charge as required.
Battery is draining quickly - Service or replace the battery.
Battery cables are disconnected or terminals are faulty - Check wiring and clean or replace terminals.
Faulty starter motor - Starter needs to be changed.
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| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
