Yamaha F70AET Troubleshooting
| Engine Model: Yamaha F70AET |
| Engine Type: 4-stroke inline 4-cylinder SOHC 16-valve gasoline outboard engine |
| Total Displacement: 60.8 cu.in (996 cc) |
| Rated Engine Power: 70 Hp (51.5 kW) at 5800 rpm |
| Fuel System: Electronic Fuel Injection (EFI) |
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| Engine difficult to start or will not start |
No fuel in fuel tank - Fill gasoline up.
Improper fuel grade - Use correct fuel grade.
Air trapped in fuel system - Bleed air.
Spark plug wiring connection is defective - Check spark plug wiring connection, repair or change.
Spark plug is faulty - Replace spark plug.
Fuel filter is plugged - Replace or clean fuel filter.
Vapor separator needle valve is bend or wear - Change vapor separator needle valve.
Fuel lines are dirty - Fuel lines need to be cleaned.
Fuel tank air vent closed or restricted - Open or service air vent.
Defective fuel feed pump - Replace or rebuild fuel feed pump.
Worn or unadjusted choke cable - Adjust correctly or change the cable.
Valve clearance is wrong - Adjustment procedure required.
Valve timing is improper - Set the valve timing properly.
Fuel pressure is low - Check system for fuel leaks or check low pressure fuel pump.
Dirty or faulty fuel injector - Clean or install new injector.
Fuel regulator malfunction - Install new fuel regulator.
Electronic control modul failure - Replace ECM.
| Engine starts but immediately stops |
Spark plug is damaged - Replace spark plug.
Vapor separator needle valve is damaged or worn - Replace needle valve.
Faulty ignition coil - Ignition coil must be replaced.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Fuel pump malfunction - Change or rebuild fuel pump.
Choke system is damaged - Change choke system components as required.
Valve clearance is improper - Adjust valve clearance according to specifications.
Incorrect valve timing - Adjust valve timing as required.
Loose or broken valve springs - New valve springs need to be installed.
Stuck valves - Valves must be cleaned.
Poor compression - Check and repair damaged parts.
Dirty fuel filter - Install new filter.
Damaged or clogged fuel injector - Clean or replace as required.
Insufficient engine oil - Fill the crankcase with engine oil.
Oil pump failure - Change oil pump as required.
Water intake is clogged - Need to wash or clean.
Thermostat is faulty - Replace thermostat.
Water pump failure - Change water pump.
Ignition failure - Check ignition and replace faulty components.
Clogged or defective fuel pump - Test fuel pump and change if necessary.
Vapor separator needle valve is bend or wear - Change vapor separator needle valve.
Fuel lines are dirty - Fuel lines need to be cleaned.
Fuel tank air vent clogged or closed - Open or service air vent.
Fuel filter is dirty - Fuel filter needs changing.
Intake manifold is air leaking - Change intake manifold gasket.
Water intake screen is dirty - Need to wash or clean.
Throttle valve and throttle link are defective or worn - Change faulty components.
Clogged or worn fuel injector - Clean or install new injector.
Engine is under excessive load - Reduce the load.
Clogged fuel pump or fuel injector - Clean or replace if necessary.
Improper ignition timing - Set the ignition timing correctly.
Thermostat is defective - Change thermostat as required.
Water pump failure - Replace water pump.
Improper propeller diameter or pitch - Install correct propeller.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard motor is positioned too low or too high - Mount the motor as required.
Lack of engine oil - Fill the crankcase with engine oil.
Faulty oil pump - Replace oil pump.
Water intake is blocked - Clean and wash as required.
Valve setting is improper - Set the valves correctly.
Stale gasoline - Change fuel.
Engine overload - Reduce engine load.
Wrong adjustment of low idle speed - Correct the settings.
Fuel pump is defective or dirty - Service or change fuel pump.
Worn main bearings or crankshaft - Repair or replace defective parts.
Cylinder bore or piston rings are damaged - Replace defective parts.
| Engine power is insufficient |
Fuel lines are clogged - Clean fuel system lines.
Fuel injector is defective - Test fuel injector and replace if necessary.
Fuel pump is dirty or defective - Test fuel pump and replace if necessary.
Defective ignition - Inspect ignition system and change failed components.
Damaged cylinder head gasket - Install new cylinder head gasket.
Powerhead components are faulty - Replace defective components as required.
Valves are burned or stuck - Replace or service valves.
Propeller pitch or diameter incorrect - Install correct propeller.
Damaged or improper size of propeller - Have propeller repaired or replaced.
Outboard engine mounting height improperly - Have motor adjusted to proper transom height.
Trim angle is incorrect - Adjust trim angle.
| Engine uses too much fuel |
Clogged or worn fuel injector - Clean or replace as required.
Faulty or loose spark plug - Tighten or replace spark plug.
Worn sleeve, rings, or piston - Replace faulty parts as required.
Electronic control unit is not operating - Change electronic control unit.
| Engine vibrates excessively |
Damaged or bent propeller - Have propeller repaired or replaced.
Propeller shaft damaged - Have propeller shaft replaced.
Weeds wraped around propeller - Remove and clean propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Loose or faulty steering pivot Tighten correctly or replace.
Battery power is low - Battery needs to be recharged.
Battery discharges quickly - Service or replace the battery.
Disconnected wiring or bad battery terminals - Connect wiring properly or install new terminals.
Faulty starter motor - Starter should be changed.
| Trim motor runs but trim system does not move up or down |
Lack of oil - Fill up oil.
Damaged pump assembly - Check pump and change if required.
Manual release valve leaking - Valve need to be closed or changed.
Motor or pump driveshaft faulty - Replace worn component.
| Trim does not fully up or down |
Pump assembly is damaged - Replace pump.
Tilt ram piston ball is in wrong position - Service or repair.
Tilt ram piston O-ring damaged - Install new O-ring.
Oil insufficient - Fill up oil.
Lower check valve not seating in port side trim ram - Secure valve properly.
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