Tohatsu MFS5B Troubleshooting
| Engine Model: Tohatsu MFS5B |
| Engine Type: 4-stroke 1-cylinder OHV gasoline outboard engine |
| Total Displacement: 7.5 cu.in (123 cc) |
| Rated Engine Power: 5 Hp (3.7 kW) at 5500 rpm |
| Fuel System: Carburetor |
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| Engine starts up hard or won't start |
No gasoline in tank - Add fuel.
Wrong fuel grade - Change gasoline.
Air in the fuel pipes - Bleed the fuel pipes.
Disconnected or loose spark plug wire - Inspect the spark plug wire connection, replace or repair.
Defective spark plug - Replace spark plug.
Fuel filter is clogged - Change fuel filter.
Incorrect carburetor adjustment - Adjust carburetor idle mixture screw.
Fuel lines are dirty - Fuel lines must be clean.
Fuel tank air vent clogged or closed - Open or clean air vent.
Defective fuel pump - Change or rebuild fuel pump.
Worn or unadjusted choke cable - Change cable or adjust correctly.
Valve clearance is incorrect - Adjust valve clearance.
Wrong valve timing - Adjust valve timing correctly.
| Engine starts but then shuts off |
Spark plug is damaged - Change spark plug.
Carburetor is defective or dirty - Clean or install new carburetor.
Ignition coil is faulty - Ignition coil should be replaced.
Closed or clogged fuel tank air vent - Open or clean air vent.
Fuel pump is faulty - Change or rebuild fuel pump.
Choke system is damaged - Check and repair choke system.
Valve clearance is wrong - Adjustment procedure required.
Valve timing is incorrect - Set the valve timing properly.
Valve springs are broken or bad - Change valve springs.
Valves sticking - Clean the valves.
| Engine runs intermittently |
Ignition system failure - Inspect ignition system and change failed components.
Clogged or damaged fuel pump - Service or change fuel pump.
Carburetor malfunction - Check and repair as required.
Dirt in the fuel lines - Service fuel lines.
Closed or restricted fuel tank air vent - Open or service air vent.
Dirty fuel filter - Replace or clean fuel filter.
Gaskets are damaged - Change gaskets.
Water intake screen is dirty - Need to clean or wash.
Damaged choke system - Check and repair choke system.
Excessive engine load - Reduce the load.
Too lean fuel mixture in carburetor - Make the correct settings.
Ignition timing is incorrect - Set the ignition timing properly.
Faulty thermostat - Change thermostat as required.
Faulty water pump - Replace water pump.
Incorrect propeller selection - Install correct propeller.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard engine is mounted too high or too low - Mount the motor as required.
Engine oil level is low - Fill the crankcase with engine oil.
Oil pump malfunction - Install new oil pump.
Clogged water intake - Need to wash or clean.
Valve setting is wrong - Valves needs to be set correctly.
Stale or low octane fuel - Use correct fuel.
Engine is under excessive load - Reduce the load.
Low idle speed set incorrectly - Adjust idling as required.
Dirty or damaged fuel pump - Service or change fuel pump.
Main bearings or crankshaft are worn out - Install new parts as as required.
Damaged cylinder bore or piston rings - Change defective components.
Carburetor is clogged or improperly adjusted - Service or correctly adjust carburetor.
Dirty or defective fuel pump - Clean or install new fuel pump.
Ignition system is defective - Inspect ignition system and change failed components.
Damaged cylinder head gasket - Replace the head gasket.
Powerhead components are damaged - Change defective components.
Burned or stuck valves - Service or change valves.
Incorrect propeller selection - Check the propeller size.
Damaged or improper size of propeller - Have propeller repaired or replaced.
Incorrect outboard motor mounting height - Check the outboard engine mounting height.
Improper trim angle - Make the correct trim angle adjustment.
| Engine uses too much fuel |
Incorrect adjustment of carburetor main jet - Adjust main jet as required.
Spark plug is loose or defective - Spark plug need to be tightened or replaced.
Sleeve, piston, or rings are damaged - Replace defective parts.
| Excessive motor vibration |
Damaged or bent propeller - Replace propeller.
Damaged propeller shaft - Propeller shaft needs to be replaced.
Weeds wraped around propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Loose or faulty steering pivot Tighten correctly or replace.
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| Outboard Engines Technical Specifications |
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