Yamaha F50LB Troubleshooting
| Engine Model: Yamaha F50LB |
| Engine Type: 4-stroke inline 4-cylinder SOHC 8-valve gasoline outboard engine |
| Total Displacement: 60.8 cu.in (996 cc) |
| Rated Engine Power: 50 Hp (36.8 kW) at 5500 rpm |
| Fuel System: Electronic Fuel Injection (EFI) |
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| Engine difficult to start or will not start |
No gasoline in tank - Add gasoline.
Improper fuel grade - Use quality fuel.
Dirt and debris in fuel system - Remove debris and dirt.
Spark plug wiring connection is damaged - Check the spark plug wire connection, repair or replace.
Faulty spark plug - Change spark plug.
Dirty fuel filter - Install new filter.
Worn or damaged vapor separator needle valve - Install new needle valve.
Restricted fuel lines - Fuel lines must be clean.
Fuel tank air vent restricted or closed - Open or service air vent.
Damaged fuel feed pump - Replace or rebuild fuel feed pump.
Improperly adjusted or worn throttle cable - Adjust correctly or change the cable.
Incorrect valve clearance - Adjust valve clearance according to specifications.
Valve timing is improper - Adjust valve timing correctly.
Fuel pressure is low - Check system for fuel leaks or check low pressure fuel pump.
Dirty or faulty fuel injector - Replace or clean as required.
Fuel regulator is not operating - Change fuel regulator.
ECM failure - Install new ECM.
| Engine starts but immediately shuts off |
Defective spark plug - Change spark plug as required.
Vapor separator needle valve is bend or wear - Install new needle valve.
Ignition coil is damaged - Install a new ignition coil.
Fuel tank air vent restricted or closed - Open or service air vent.
Fuel pump defective - Change or rebuild fuel pump.
Choke system is damaged - Change choke system components as required.
Valve clearance is not correct - Adjustment procedure required.
Wrong valve timing - Set the valve timing properly.
Bad or broken valve springs - Install new valve springs.
Stuck valves - Valves need to be cleaned.
Poor compression - Inspect and replace defective parts.
Fuel filter is clogged - Fuel filter needs changing.
Fuel injector is faulty or clogged - Clean or replace as required.
Engine oil level is insufficient - Add oil to the engine crankcase.
Defective oil pump - Install new oil pump.
Water intake is blocked - Wash or clean as required.
Thermostat failure - Install new thermostat.
Water pump is defective - Replace water pump.
| Engine runs intermittently |
Ignition system problems - Inspect ignition system and change failed components.
Fuel pump is dirty or defective - Inspect fuel pump and change as required.
Vapor separator needle valve is worn or defective - Replace needle valve.
Fuel lines are dirty - Fuel lines must be clean.
Fuel tank air vent restricted or closed - Open or service air vent.
Clogged fuel filter - Change fuel filter.
Intake manifold is air leaking - Replace intake manifold gasket.
Dirty water intake screen - Need to clean or wash.
Throttle valve and throttle link are defective or worn - Change faulty components.
Damaged or clogged fuel injector - Clean or install new injector.
Engine is under excessive load - Load reducing required.
Fuel injector or fuel pump is dirty - Replace or clean if necessary.
Wrong ignition timing - Adjust ignition timing as required.
Thermostat is defective - Change thermostat as required.
Water pump is defective - Install new water pump.
Improper propeller diameter or pitch - Replace propeller.
Propeller bent or damaged - Have propeller repaired or replaced.
Outboard engine is mounted too high or too low - Mount the motor as required.
Engine oil insufficient - Fill up the engine oil.
Defective oil pump - Oil pump need to be replaced.
Dirty water intake screen - Clean and wash as required.
Valve setting is improper - Valves needs to be set correctly.
Low octane gasoline - Use correct fuel.
Engine is running overloaded - Reduce load.
Low idle speed adjustment is incorrect - Adjust the low idle speed.
Dirty or faulty fuel pump - Clean or replace fuel pump.
Main bearings or crankshaft wear - Need to install new components.
Cylinder bore or piston rings are worn - Change defective parts.
Restricted fuel lines - Clean fuel lines.
Fuel injector malfunction - Inspect fuel injector and change as required.
Fuel pump is faulty or clogged - Check fuel pump and replace if necessary.
Ignition system is defective - Check ignition system and replace faulty parts.
Cylinder head gasket is defective - Replace the head gasket.
Worn powerhead parts - Change defective components.
Burned or stuck valves - Service or change valves.
Improper propeller diameter or pitch - Check the propeller size.
Propeller bent or damaged - Have propeller repaired or replaced.
Engine mounted at wrong transom height - Have motor adjusted to proper transom height.
Trim angle is incorrect - Adjust trim angle.
| Engine uses too much fuel |
Fuel injector is damaged or dirty - Clean or replace as required.
Defective or loose spark plug - Change or re-tighten spark plug.
Worn rings, piston, or sleeve - Replace defective parts.
ECU is faulty - Change electronic control unit.
| Excessive motor vibration |
Damaged or improper size of propeller - Replace propeller.
Propeller shaft malfunction - Replace propeller shaft.
Weeds clogs the propeller - Clean the propeller.
Engine mounting bolt is not tightened - Tighten bolt.
Steering pivot is loose or damaged Tighten or replace.
Low battery voltage - Battery is drained, charge it.
Battery does not hold charge - Service or replace the battery.
Battery terminals are corroded or wires are disconnected - Check wiring and clean or replace terminals.
Damaged starter motor - Replace or repair starter.
| Trim motor runs but trim system does not move up or down |
Oil level is low - Fill up oil to required level.
Pump assembly faulty - Check pump and change if required.
Leakage of manual drain valve - Close the valve or change it.
Pump driveshaft or motor damaged - Replace defective component.
| Trim does not fully up or down |
Damaged pump assembly - Change pump.
Tilt ram piston ball is in wrong position - Clean or repair.
Tilt ram piston O-ring damaged - Change O-ring.
Oil level low - Fill up oil.
Lower check valve not seating in port side trim ram - Install valve correctly.
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