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| Home / Outboard Engines / Tohatsu Engines / Tohatsu M9.8B |
Tohatsu M9.8B Troubleshooting
The Tohatsu M9.8B is a 2-stroke 2-cylinder forced water-cooled shallow-water drive gasoline outboard engine with a rated power of 9.8 hp (7.2 kW) at 5000-6000 rpm. The engine cylinder bore is 1.97" (50 mm) and piston stroke is 1.69" (43 mm). A 10.3 cubic inches (169 cc) outboard motor has a carburetor fuel system, starting system with manual starter, flywheel magneto capacitor discharge ignition system, dog clutch shift system, manual tilt, and handle tiller or remote control steering. The fuel tank capacity is 3.2 gal (12 liters). The propeller is made of aluminum and it has three blades.
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| Engine will not start or hard to start |
No fuel in fuel tank - Fill fuel up.
Low-quality gasoline - Change fuel.
Fuel system clogged - Repair or replace.
Spark plug wiring connection is damaged - Check spark plug wiring connection, repair or change.
Spark plug is damaged - Install new spark plug.
Clogged fuel filter - Change fuel filter.
Incorrect carburetor adjustment - Adjust carburetor idle mixture screw.
Dirty fuel lines - Service fuel lines.
Fuel tank air vent restricted or closed - Open or service air vent.
Lack of fuel pump pressure - Replace or rebuild fuel pump.
Reed valve is defective or worn - Install new reed valve.
| Engine starts but stalls immediately |
Spark plug is faulty - Replace spark plug.
Faulty or clogged carburetor - Service or replace carburetor.
Ignition coil is damaged - Ignition coil must be replaced.
Fuel tank air vent restricted or closed - Open or clean air vent.
Low fuel pump pressure - Replace or repair fuel pump.
| Engine runs unevenly |
Ignition system problems - Check ignition and replace faulty components.
Dirty or damaged fuel pump - Test fuel pump and replace if necessary.
Carburetor incorrectly set - Set carb correctly.
Fuel lines clogging - Service fuel lines.
Fuel tank air vent restricted or closed - Open or service air vent.
Clogged fuel filter - Replace fuel filter.
Gaskets are worn - Install new gaskets.
| Engine overheated |
Excessive engine load - Load reducing is recommended.
Carburetor mixture is too lean - Set the carburetor correctly.
Bad ignition timing - Adjust ignition timing correctly.
Damaged thermostat - Change thermostat.
Faulty water pump - Install new water pump.
Incorrect propeller selection - Install correct propeller.
Damaged or improper size of propeller - Replace propeller.
Outboard motor is mounted too high or too low - Position the engine correctly.
| Engine noise or knocking |
Low octane gasoline - Change gasoline.
Engine overload - Reduce engine load.
Low idle speed setting is not correct - Adjust as required.
Fuel pump is damaged or dirty - Test fuel pump and replace if necessary.
Worn main bearings or crankshaft - Repair or replace defective parts.
Piston rings or cylinder bore are damaged - Change faulty components.
| Engine power loss |
Carburetor is clogged or improperly adjusted - Clean or correctly adjust carburetor.
Clogged or damaged fuel pump - Inspect fuel pump and change as required.
Ignition failure - Inspect ignition system and change failed components.
Damaged gaskets - Change gaskets.
Powerhead components are faulty - Replace defective parts as required.
Improper propeller diameter or pitch - Install correct propeller.
Propeller bent or damaged - Replace propeller.
Outboard engine mounting height improperly - Check the outboard engine mounting height.
Improper trim angle - Make the correct trim angle adjustment.
| Engine using too much gasoline |
Improper carburetor main jet adjustment - Adjust it correctly.
Spark plug is faulty or loose - Tighten or change the spark plug.
Rings, sleeve, or piston are damaged - Change defective parts.
| Excessive engine vibration |
Propeller bent or damaged - Have propeller repaired or replaced.
Propeller shaft malfunction - Propeller shaft needs to be replaced.
Weeds clogs the propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten bolt.
Steering pivot is loose or damaged Tighten or replace.
| Starter motor is not working |
Low battery output voltage - Charge the battery.
Battery does not hold charge - Service charging system or install new battery.
Faulty battery terminals or disconnected cables - Check cables and clean or change terminals.
Starter motor failing - Replace or repair starter.
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