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Mercury EFI 150 Troubleshooting

Engine Model: Mercury EFI 150 Hp
Engine Type: 2-cycle 6-cylinder gasoline outboard engine
Total Displacement: 153 (2507 cc)
Rated Engine Power: 150 Hp (111.8 kW) at 5750 rpm
Fuel System: Electronic fuel injection (EFI)


Engine hard starting or not starting

Empty fuel tank - Fill fuel up.
Low-quality gasoline - Change fuel.
Clogged fuel system - Remove clogging.
Damaged spark plug wiring connection - Check spark plug wiring connection, repair or change.
Spark plug is damaged - Spark plug need to be replaced.
Fuel filter is clogged - Fuel filter needs changing.
Dirty fuel lines - Clean fuel system lines.
Drained or defective battery - Recharge or replace battery.
Damaged electrical wire harness - Check wiring harness connections.
Ignition system is damaged - Change defective parts.
Pulse fuel pump is defective - Change pulse fuel pump as required.
Electric fuel pump failure - Change electric fuel pump as required.
ECM failure - Replace ECM.

Engine starts but then shuts off

Damaged spark plug - Spark plug need to be replaced.
Damaged ignition coil - Install a new ignition coil.
Defective pulse fuel pump - Change pulse fuel pump.
Fuel system is clogged - Service fuel system.
Final fuel filter is plugged - Replace or clean final filter.
Defective electric fuel pump - Change electric fuel pump as required.

Irregular engine running

Defective ignition system - Inspect ignition system and change failed components.
Clogged or defective fuel pump - Clean or replace fuel pump.
Fuel lines are clogged - Fuel lines need to be cleaned.
Dirty fuel filter - Replace fuel filter.

Engine overheats

Excessive engine load - Reduce engine load.
Incorrect ignition timing - Set the ignition timing properly.
Defective thermostat - Thermostat need to be replaced.
Water pump malfunction - Replace water pump.

Engine knocking or noise

Stale gasoline - Use proper gasoline.
Excessive engine load - Reduce the load.
Low idle speed setting is incorrect - Adjustment required.
Fuel pump is damaged or dirty - Check fuel pump and change if required.
Main bearings or crankshaft failure - Need to install new components.
Cylinder bore or piston rings are damaged - Replace faulty parts.

Low engine power

Dirty or damaged fuel pump - Check fuel pump and replace if necessary.
Ignition system problems - Check ignition system and replace faulty parts.
Worn powerhead components - Replace defective parts as required.
Failed switch box, stator, or coil - Replace faulty parts.
Bad compression - Normalize compression.
Fuel delivery problem - Check and repair.
Manifold fuel leak - Leak must be repaired.
Vapor separator is flooded - Normalize vapor separator functions.

Engine uses too much fuel

Spark plug is faulty or loose - Re-tighten or replace spark plug.
Worn piston, rings, or sleeve - Change defective parts.
Excessive engine load - Reduce the load.
Dirty or defective fuel injectors - Clean or replace fuel injectors.

Trim motor is running but system can't move

Oil level is low - Fill up oil to required level.
Pump assembly faulty - Inspect pump and change as required.
Manual release valve leaking - Valve need to be closed or changed.
Pump driveshaft or motor damaged - Change defective component.

Trim does not fully up or down

Defective pump assembly - Replace pump.
Tilt ram piston ball is not positioned correctly - Clean or repair.
Damaged tilt ram piston O-ring - Replace O-ring.
Low oil level - Fill up oil.
Lower check valve not seating in port side trim ram - Install valve correctly.