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| Home / Outboard Engines / Mercury Engines / Mercury 20 MH |
Mercury 20 MH Troubleshooting
| Engine doesn't start or starts hard |
Gas tank is empty - Fill gasoline up.
Wrong fuel grade - Use quality fuel.
Air in fuel tank - Bleed fuel tank.
Faulty spark plug wire connection - Inspect spark plug wiring connection, change or repair.
Faulty spark plug - Change spark plug.
Dirty fuel filter - Replace or clean fuel filter.
Fuel lines clogging - Clean fuel system lines.
Drained or worn battery - Charge or change the battery.
Damaged wiring harness connections - Check wiring harness connections.
Ignition system is damaged - Check ignition components and replace if necessary.
Pulse fuel pump is faulty - Change pulse fuel pump as required.
Damaged electric fuel pump - Install new electric fuel pump.
ECM failure - Install new ECM.
| Engine stalls after starting |
Defective spark plug - Spark plug need to be replaced.
Defective ignition coil - Ignition coil must be replaced.
Pulse fuel pump is faulty - Replace pulse fuel pump.
Restrictions in fuel system - Fuel system need to be cleaned.
Final fuel filter is clogged - Replace fuel filter.
Damaged electric fuel pump - Electric fuel pump need to be replaced.
| Engine runs unevenly |
Ignition system problems - Inspect ignition system and change failed components.
Dirty or faulty fuel pump - Inspect fuel pump and change as required.
Dirty fuel lines - Clean fuel system lines.
Fuel filter is plugged - Replace or clean fuel filter.
| Engine overheated |
Engine overloaded - Load reducing required.
Wrong ignition timing - Adjust ignition timing correctly.
Thermostat is faulty - Install new thermostat.
Faulty water pump - Change water pump.
| Abnormal engine knocking or noise |
Stale or low octane fuel - Change gasoline.
Engine is overloaded - Load reducing required.
Low idle speed setting is incorrect - Adjustment required.
Fuel pump is clogged or faulty - Check fuel pump and replace if necessary.
Main bearings or crankshaft failure - Change or repair worn components.
Piston rings or cylinder bore are damaged - Replace faulty parts.
| Low engine power |
Dirty or defective fuel pump - Service or replace fuel pump.
Ignition failure - Inspect ignition system and change failed components.
Worn powerhead parts - Change defective components.
Stator, coil, or switch box defective - Change faulty components.
Bad compression - Correct.
Fuel delivery problem - Check and repair.
Manifold is leaking - Repair leaks.
Vapor separator flooding over - Check and correct malfunction.
| Engine uses too much fuel |
Loose or faulty spark plug - Re-tighten or replace spark plug.
Worn sleeve, rings, or piston - Replace faulty parts.
Engine is running overloaded - Reduce engine load.
Fuel injectors are clogged or faulty - Service or change fuel injectors.
| Trim motor runs but system does not move |
Oil level is low - Need to add the oil.
Defective pump assembly - Inspect pump and change as required.
Manual shut-off valve leaks - Close the valve fully or replace it.
Broken motor or pump driveshaft - Change defective component.
| Trim cannot be fully up or down |
Pump assembly faulty - Replace pump.
Tilt ram piston ball is displaced - Clean or repair.
Tilt ram piston O-ring damaged - Install new O-ring.
Oil level is insufficient - Need to add the oil.
Lower check valve not seating in port side trim ram - Secure valve properly.
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| Engines Technical Specifications |