Mercury 300 L6 Verado Problems
| Engine Model: Mercury Verado 300 L6 |
| Engine Type: 4-stroke inline 6-cylinder supercharger gasoline outboard engine |
| Total Displacement: 158 cu.in (2.6 L) |
| Rated Engine Power: 300 Hp (224 kW) at 6400 rpm |
| Fuel System: Sequential multi-point electronic fuel injection (EFI) |
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| Engine is not starting or hard starting |
Fuel tank is empty - Add fuel.
Wrong grade of gasoline - Change gasoline.
Water or air in fuel system - Remove air or water from system.
Defective spark plug wire connection - Inspect the spark plug wire connection, replace or repair.
Faulty spark plug - Change spark plug as required.
Dirty fuel filter - Install new filter.
Worn or defective vapor separator needle valve - Install new needle valve.
Fuel lines are dirty - Clean fuel system lines.
Fuel tank air vent clogged or closed - Open or service air vent.
Fuel feed pump malfunction - Install new feed pump or repair it.
Incorrectly adjusted or damaged throttle cable - Change cable or adjust correctly.
Valve clearance is not correct - Adjust valve clearance.
Improper valve timing - Set the valve timing correctly.
Low fuel pressure - Check system for fuel leaks or check low pressure fuel pump.
Fuel injector is damaged or dirty - Clean or install new injector.
Fuel regulator is faulty - Replace fuel regulator.
Electronic control modul failure - Replace ECM.
| Engine starts and stalls immediately |
Faulty spark plug - Change spark plug.
Damaged or wear vapor separator needle valve - Install new needle valve.
Faulty ignition coil - Change ignition coil as required.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Defective fuel pump - Repair or change fuel pump.
Damaged choke system - Inspect and replace choke system components.
Valve clearance is incorrect - Adjust valve clearance according to specifications.
Valve timing is wrong - Set the valve timing correctly.
Valve springs are worn or loose - Install new valve springs.
Valves sticking - Valves need to be cleaned.
Bad cylinder compression - Check and replace worn parts.
Dirty fuel filter - Replace fuel filter.
Fuel injector is damaged or dirty - Replace or clean as required.
Not enough engine oil - Need to add engine oil.
Oil pump failure - Install new oil pump.
Water intake is blocked - Need to clean or wash.
Defective thermostat - Install new thermostat.
Water pump malfunction - Replace water pump.
Ignition system is defective - Check ignition system and replace faulty parts.
Dirty or damaged fuel pump - Clean or replace fuel pump.
Worn or damaged vapor separator needle valve - Install new needle valve.
Dirt in the fuel lines - Fuel lines must be clean.
Closed or restricted fuel tank air vent - Open or clean air vent.
Fuel filter is plugged - Change fuel filter.
Intake manifold air leaks - Install new gasket.
Water intake is clogged - Need to clean or wash.
Throttle valve and throttle link are damaged or worn - Replace faulty components.
Fuel injector is clogged or malfunction - Clean or install new injector.
Engine overload - Reduce engine load.
Fuel injector or fuel pump is clogged - Replace or clean if necessary.
Ignition timing is incorrect - Set the ignition timing properly.
Thermostat is defective - Install new thermostat.
Faulty water pump - Change water pump as required.
Incorrect propeller selection - Replace propeller.
Damaged or improper size of propeller - Have propeller repaired or replaced.
Outboard motor is mounted too high or too low - Mount the motor as required.
Low engine oil level - Fill the crankcase with engine oil.
Faulty oil pump - Change oil pump.
Water intake is blocked - Need to wash or clean.
Wrong valve setting - Set the valves correctly.
| Abnormal engine knocking or noise |
Stale gasoline - Change fuel.
Engine overloaded - Reduce engine load.
Incorrect low idle setting - Need to adjust idle speed.
Fuel pump is defective or dirty - Check fuel pump and change if required.
Crankshaft or main bearings failure - Change or repair worn components.
Worn piston rings or cylinder bore - Replace defective components.
Dirty fuel lines - Fuel lines must be clean.
Defective fuel injector - Check fuel injector and change if required.
Fuel pump is faulty or clogged - Test fuel pump and replace if necessary.
Ignition failure - Inspect ignition system and change failed components.
Damaged cylinder head gasket - Install new cylinder head gasket.
Powerhead components are worn - Replace defective components as required.
Stuck or burned valves - Change or service valves.
Incorrect propeller selection - Install correct propeller.
Propeller bent or damaged - Replace propeller.
Outboard engine mounting height improperly - Have motor adjusted to proper transom height.
Incorrect trim angle - Adjust trim angle correctly.
| Engine using too much gasoline |
Dirty or faulty fuel injector - Clean or replace as required.
Spark plug is defective or loose - Tighten or change the spark plug.
Worn sleeve, rings, or piston - Replace faulty parts as required.
Electronic control unit is not operating - Change electronic control unit.
Damaged or improper size of propeller - Replace propeller.
Damaged propeller shaft - Replace propeller shaft.
Weeds clogs the propeller - Remove and clean propeller.
Engine mounting bolt is not tightened - Tighten bolt.
Steering pivot is faulty or loose Tighten correctly or replace.
Low battery voltage - Battery needs to be recharged.
Battery discharges quickly - Battery needs to be serviced or replaced.
Battery cables are disconnected or terminals are faulty - Connect cables properly or replace terminals.
Faulty starter motor - Starter needs to be changed.
| Trim motor is running but trim system cannot move up or down |
Lack of oil - Need to add the oil.
Defective pump assembly - Test pump and replace if necessary.
Manual shut-off valve leaks - Close the valve fully or replace it.
Faulty pump driveshaft or motor - Change worn component.
| Trim does not fully up or down |
Pump assembly is faulty - Change pump as required.
Tilt ram piston ball is not positioned correctly - Clean or repair.
Tilt ram piston O-ring is worn - Replace O-ring.
Not enough oil - Fill up oil to required level.
Lower check valve not seating in port side trim ram - Secure valve properly.
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