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Mercury EFI 175 Troubleshooting

Engine Model: Mercury EFI 175 Hp
Engine Type: 2-cycle 6-cylinder gasoline outboard engine
Total Displacement: 153 (2507 cc)
Rated Engine Power: 175 Hp (130.5 kW) at 5750 rpm
Fuel System: Electronic fuel injection (EFI)


Engine doesn't start or hard to start

No fuel in fuel tank - Add fuel.
Wrong grade of gasoline - Use quality fuel.
Dirty fuel system - Check and clean.
Faulty spark plug wire connection - Inspect the spark plug wire connection, replace or repair.
Faulty spark plug - Install new spark plug.
Fuel filter is clogged - Fuel filter needs changing.
Fuel lines are clogged - Fuel lines must be clean.
Discharged or worn battery - Change or recharge battery.
Damaged wiring harness connections - Inspect harness connections.
Ignition system malfunction - Replace defective components.
Pulse fuel pump is defective - Replace pulse fuel pump.
Electric fuel pump failure - Electric fuel pump need to be replaced.
Electronic control modul failure - Replace ECM.

Engine starts and immediately shuts off

Damaged spark plug - Install new spark plug.
Ignition coil is faulty - Change ignition coil as required.
Pulse fuel pump failure - Pulse fuel pump need to be replaced.
Fuel system clogging - Clean fuel system.
Dirty final fuel filter - Final filter needs changing.
Electric fuel pump failure - Install new electric fuel pump.

Engine runs intermittently

Ignition system failure - Check ignition system and replace faulty parts.
Fuel pump is clogged or faulty - Test fuel pump and change if necessary.
Fuel lines are dirty - Fuel lines must be clean.
Fuel filter is clogged - Install new filter.

Engine is overheated

Engine is overloaded - Reduce load.
Bad ignition timing - Ignition timing needs to be set properly.
Thermostat failure - Install new thermostat.
Defective water pump - Water pump need to be replaced.

Engine knocks or noises

Stale or low octane fuel - Use correct fuel.
Engine is running overloaded - Reduce engine load.
Low idle speed adjustment is incorrect - Correct idle settings.
Clogged or damaged fuel pump - Clean or install new fuel pump.
Crankshaft or main bearings failure - Have bearings or crankshaft replaced.
Damaged cylinder bore or piston rings - Change defective parts.

Engine power loss

Dirty or damaged fuel pump - Service or change fuel pump.
Defective ignition - Check ignition system and replace faulty parts.
Faulty powerhead parts - Change defective parts.
Stator, coil, or switch box defective - Replace damaged components.
Compression is insufficient - Normalize compression.
Fuel delivery problem - Check fuel system.
Manifold fuel leak - Leak must be repaired.
Vapor separator is flooded - Normalize vapor separator functions.

Engine using too much gasoline

Faulty or loose spark plug - Re-tighten or replace spark plug.
Rings, sleeve, or piston are damaged - Change faulty parts.
Engine is overloaded - Load reducing required.
Dirty or damaged fuel injectors - Check fuel injectors and change if required.

Trim motor runs but system does not move

Not enough oil - Check oil level and add oil as required.
Defective pump assembly - Check pump and change if required.
Leakage of manual drain valve - Close the valve fully or replace it.
Broken motor or pump driveshaft - Change worn component.

Trim does not fully up or down

Damaged pump assembly - Change pump as required.
Tilt ram piston ball is not positioned correctly - Clean or repair.
Damaged tilt ram piston O-ring - Change O-ring.
Insufficient oil - Checking oil level and add if necessary.
Lower check valve is not properly secured in port side trim ram - Install valve correctly.