Mercury 25 Jet 4 stroke Problems
| Engine Model: Mercury Jet 25 |
| Engine Type: 4-stroke inline 3-cylinder SOHC gasoline outboard engine |
| Total Displacement: 32.1 cu.in (0.5 L) |
| Rated Engine Power: 25 Hp (18.4 kW) at 5500 rpm |
| Fuel System: Electronic Fuel Injection (EFI) |
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| Engine starts up hard or will not start |
No fuel in fuel tank - Fill gasoline up.
Incorrect fuel grade - Change gasoline.
Air or water in fuel system - Remove water or air from fuel system.
Spark plug wire is loose or disconnected - Inspect spark plug wiring connection, change or repair.
Spark plug is damaged - Install new spark plug.
Dirty fuel filter - Fuel filter needs changing.
Vapor separator needle valve is damaged or worn - Install new needle valve.
Dirt in the fuel lines - Service fuel lines.
Fuel tank air vent closed or restricted - Open or service air vent.
Damaged fuel feed pump - Replace or rebuild fuel feed pump.
Damaged or incorrectly adjusted choke cable - Adjust properly or change the cable.
Excessive valve clearance - Need to adjust valve clearance.
Valve timing is incorrect - Set the valve timing properly.
Low fuel pressure - Inspect low pressure fuel pump or inspect fuel system for leaks.
Fuel injector is damaged or dirty - Clean or replace as required.
Fuel regulator is defective - Change fuel regulator.
ECM is not functioning - Replace ECM.
| Engine starts and then stalls |
Faulty spark plug - Replace spark plug.
Vapor separator needle valve is worn or defective - Install new needle valve.
Ignition coil is defective - Ignition coil should be replaced.
Fuel tank air vent closed or restricted - Open or clean air vent.
Defective fuel pump - Repair or change fuel pump.
Faulty choke system - Inspect and replace choke system components.
Improper valve clearance - Adjustment procedure required.
Wrong valve timing - Set the valve timing correctly.
Valve springs are loose or broken - Replace valve springs.
Valves sticking - Service the valves.
Poor cylinder compression - Check and change damaged parts.
Clogged fuel filter - Change fuel filter.
Fuel injector is damaged or dirty - Clean or install new injector.
Engine oil insufficient - Check oil level and add oil as required.
Defective oil pump - Install new oil pump.
Clogged water intake - Wash or clean as required.
Damaged thermostat - Replace thermostat.
Damaged water pump - Change water pump.
| Engine runs intermittently |
Ignition failure - Test ignition and replace failed parts.
Clogged or damaged fuel pump - Clean or replace fuel pump.
Vapor separator needle valve is damaged or worn - Change vapor separator needle valve.
Fuel lines are clogged - Service fuel lines.
Closed or restricted fuel tank air vent - Open or clean air vent.
Fuel filter is clogged - Fuel filter needs changing.
Intake manifold air leaks - Install new gasket.
Water intake is blocked - Clean and wash as required.
Throttle link and throttle valve are wear or damaged - Replace faulty parts.
Clogged or worn fuel injector - Clean or replace as required.
Engine overload - Load reducing is recommended.
Fuel pump or fuel injector is dirty - Replace or clean as required.
Ignition timing is incorrect - Ignition timing needs to be adjusted correctly.
Thermostat failure - Install new thermostat.
Water pump malfunction - Change water pump as required.
Propeller pitch or diameter incorrect - Check the propeller size.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard motor is mounted too high or too low - Mount the motor as required.
Engine oil insufficient - Fill up the engine oil.
Faulty oil pump - Replace oil pump.
Clogged water intake - Clean and wash as required.
Wrong valve setting - Set the valves properly.
Stale fuel - Use correct gasoline.
Engine is overloaded - Reduce engine load.
Too low idle RPM - Adjust as required.
Clogged or defective fuel pump - Check fuel pump and replace if necessary.
Crankshaft or main bearings are worn out - Need to install new components.
Piston rings or cylinder bore are worn - Replace faulty parts.
Fuel lines are clogged - Fuel lines need to be cleaned.
Fuel injector is defective - Check fuel injector and replace if necessary.
Dirty or defective fuel pump - Service or change fuel pump.
Ignition system problems - Inspect ignition system and change failed components.
Blown cylinder head gasket - Change cylinder head gasket.
Damaged powerhead components - Change defective components.
Valves are stuck or burned - Replace or service valves.
Propeller selection improperly - Install correct propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Engine mounted at wrong transom height - Adjust the engine to correct transom height.
Trim angle is incorrect - Adjust trim angle correctly.
| Engine using too much gasoline |
Clogged or worn fuel injector - Clean or replace as required.
Spark plug is faulty or loose - Re-tighten or replace spark plug.
Sleeve, piston, or rings are damaged - Replace defective parts as required.
Electronic control unit is not operating - Replace ECU.
| Excessive motor vibration |
Propeller bent or damaged - Have propeller repaired or replaced.
Propeller shaft malfunction - Replace propeller shaft.
Weeds in the propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Damaged or loose steering pivot Tighten or replace.
Low battery output voltage - Battery is drained, recharge it.
Battery will not hold charge - Service charging system or change battery.
Wires are disconnected or battery terminals are corroded - Check cables and clean or change terminals.
Starter motor is faulty - Starter should be changed.
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