Mercury 150 Pro XS Troubleshooting
| Engine Model: Mercury Pro XS 150 |
| Engine Type: 4-stroke inline 4-cylinder SOHC 8-valve gasoline outboard engine |
| Total Displacement: 183 cu.in (3 L) |
| Rated Engine Power: 150 Hp (110 kW) at 6000 rpm |
| Fuel System: Multi-Point Electronic Fuel Injection (EFI) |
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| Engine starts up hard or doesn't start |
No gasoline in tank - Add fuel.
Wrong fuel grade - Use correct gasoline grade.
Dirt and debris in fuel system - Remove debris and dirt.
Spark plug wire is disconnected or loose - Inspect spark plug wiring connection, change or repair.
Spark plug is damaged - Change spark plug.
Fuel filter is clogged - Change fuel filter.
Damaged or wear vapor separator needle valve - Change vapor separator needle valve.
Restricted fuel lines - Fuel lines must be clean.
Closed or restricted fuel tank air vent - Open or service air vent.
Fuel feed pump malfunction - Change or rebuild fuel feed pump.
Worn or improperly adjusted choke cable - Adjust properly or change the cable.
Valve clearance is improper - Adjustment procedure required.
Valve timing is wrong - Adjust valve timing correctly.
Low fuel pressure - Check system for fuel leaks or check low pressure fuel pump.
Dirty or faulty fuel injector - Replace or clean if necessary.
Fuel regulator is defective - Install new fuel regulator.
ECM is not functioning - Install new ECM.
| Engine starts but then shuts off |
Damaged spark plug - Change spark plug.
Worn or damaged vapor separator needle valve - Replace needle valve.
Faulty ignition coil - Replace ignition coil as necessary.
Closed or clogged fuel tank air vent - Open or service air vent.
Fuel pump defective - Install new pump or repair it.
Choke system malfunction - Check and repair choke system.
Improper valve clearance - Adjust valve clearance.
Valve timing is incorrect - Set the valve timing correctly.
Broken or bad valve springs - Valve springs need to be changed.
Stuck valves - Clean the valves.
Weak cylinder compression - Inspect and replace defective parts.
Clogged fuel filter - Fuel filter needs changing.
Fuel injector is faulty or clogged - Clean or install new injector.
Engine oil level is low - Fill the crankcase with engine oil.
Oil pump malfunction - Change oil pump.
Water intake is blocked - Wash or clean as required.
Faulty thermostat - Install new thermostat.
Water pump failure - Change water pump as required.
Ignition system failure - Test ignition and replace failed parts.
Dirty or damaged fuel pump - Service or replace fuel pump.
Damaged or wear vapor separator needle valve - Install new needle valve.
Dirt in the fuel lines - Fuel lines need to be cleaned.
Fuel tank air vent restricted or closed - Open or clean air vent.
Fuel filter is plugged - Replace or clean fuel filter.
Intake manifold is air leaking - Install new gasket.
Clogged water intake - Clean and wash as required.
Throttle link and throttle valve are worn or damaged - Change faulty components.
Fuel injector is faulty or clogged - Clean or install new injector.
Engine is overloaded - Load reducing is recommended.
Fuel injector or fuel pump is clogged - Replace or clean as required.
Ignition timing is improper - Set the ignition timing properly.
Faulty thermostat - Change thermostat.
Water pump failure - 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 positioned too low or too high - Position the engine correctly.
Insufficient engine oil - Need to add engine oil.
Oil pump is defective - Replace oil pump.
Dirty water intake screen - Need to wash or clean.
Incorrect valve setting - Adjust valves correctly.
| Abnormal engine knocking or noise |
Stale fuel - Use correct gasoline.
Engine overload - Load reducing is recommended.
Low idle speed setting is not correct - Correct idle settings.
Dirty or damaged fuel pump - Clean or install new fuel pump.
Worn main bearings or crankshaft - Worn parts replacement required.
Damaged piston rings or cylinder bore - Replace faulty components.
| Engine power is insufficient |
Fuel lines clogging - Fuel lines need to be cleaned.
Fuel injector malfunction - Replace fuel injector.
Dirty or damaged fuel pump - Check fuel pump and replace if necessary.
Ignition system is defective - Check ignition system and replace faulty parts.
Damaged cylinder head gasket - Replace the gasket as required.
Worn powerhead components - Change defective components.
Stuck or burned valves - Change or clean valves.
Improper propeller diameter or pitch - Replace propeller.
Damaged or improper size of propeller - Replace propeller.
Engine mounted at wrong transom height - Check the outboard motor mounting height.
Improper trim angle - Adjust trim angle.
Damaged or clogged fuel injector - Clean or replace as required.
Loose or faulty spark plug - Tighten or replace spark plug.
Sleeve, piston, or rings are damaged - Change faulty parts.
ECU is not functioning - Change electronic control unit.
| Excessive engine vibration |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft damaged - Have propeller shaft replaced.
Weeds clogs the propeller - Remove and clean propeller.
Motor mounting bolt is loose - Tighten bolt.
Steering pivot is faulty or loose Tighten or replace.
Low battery output - Battery is drained, charge it.
Battery is draining quickly - Service battery or change it.
Disconnected wiring or bad battery terminals - Check cable connections and replace or service terminals.
Faulty starter motor - Replace or repair starter.
| Trim motor runs but trim system does not move up or down |
Oil level is low - Checking oil level and add if necessary.
Pump assembly is faulty - Check pump and replace if necessary.
Leakage of manual release valve - Valve need to be closed or changed.
Motor or pump driveshaft faulty - Replace worn component.
| Trim cannot be fully up or down |
Defective pump assembly - Change pump as required.
Tilt ram piston ball is not positioned correctly - Service or repair.
Tilt ram piston O-ring damaged - Change O-ring.
Oil level low - Check and refill oil.
Lower check valve is not properly secured in port side trim ram - Install valve correctly.
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