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| Home / Outboard Engines / Tohatsu Engines / Tohatsu M9.9D2 |
Tohatsu M9.9D2 Troubleshooting
The Tohatsu M9.9D2 is a two-stroke two-cylinder gasoline outboard engine. This engine has a carburetor fuel system, forced water cooling with thermostat, and flywheel magneto CDI ignition system. A 15.1 cu.in (247 cc) outboard motor has a cylinder bore of 2.17" (55 mm), piston stroke of 2.05" (52 mm), and maximum power of 9.9 hp (7.3 kW) at 4500-5300 rpm. The boat motor is equipped with a dog clutch shifting, manual starting system, 3-blades aluminum standard propeller, manual trim and tilt, and tiller handle steering system. The fuel tank has a capacity of 6.6 gal (25 liters).
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| Engine starts up hard or doesn't start |
No fuel in fuel tank - Fill it up.
Low-quality gasoline - Change fuel.
Air or water in fuel system - Remove water or air from fuel system.
Defective spark plug wire connection - Inspect spark plug wiring connection, change or repair.
Defective spark plug - Spark plug need to be replaced.
Fuel filter is dirty - Replace fuel filter.
Carburetor components worn out - Repair or replace parts.
Dirty fuel lines - Service fuel lines.
Closed or clogged fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Fuel pump pressure is low - Install new fuel pump or rebuild it.
Worn or defective reed valve - Replace reed valve.
| Engine starts and stops immediately |
Damaged spark plug - Replace spark plug.
Carburetor is dirty or faulty - Clean or install new carburetor.
Ignition coil is defective - Install a new ignition coil.
Fuel tank air vent clogged or closed - Fuel tank air vent need to be opened or cleaned.
Low fuel pump pressure - Install new fuel pump or rebuild it.
| Engine runs intermittently |
Ignition system failure - Inspect ignition system and change failed components.
Clogged or damaged fuel pump - Inspect fuel pump and change as required.
Carburetor problems - Carburetor diagnostics required.
Restricted fuel lines - Service fuel lines.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Plugged fuel filter - Change fuel filter.
Gaskets are worn - Replace gaskets.
| Engine overheating |
Engine is running overloaded - Reduce load.
Too lean fuel mixture in carburetor - Set the carburetor correctly.
Ignition timing is improper - Adjust ignition timing correctly.
Damaged thermostat - Replace thermostat.
Water pump is defective - Install new water pump.
Improper propeller diameter or pitch - Install correct propeller.
Damaged or bent propeller - Replace propeller.
Outboard engine is mounted too high or too low - Position the engine correctly.
| Engine knocks or noises |
Low octane fuel - Use correct fuel.
Excessive engine load - Reduce the load.
Low idle speed adjustment is incorrect - Adjust idling as required.
Dirty or defective fuel pump - Clean or install new fuel pump.
Worn main bearings or crankshaft - Need to install new components.
Cylinder bore or piston rings are worn - Replace defective parts.
| Engine power is insufficient |
Dirty or incorrectly adjusted carburetor - Adjust the carburetor properly or clean it.
Fuel pump is clogged or faulty - Clean or replace fuel pump.
Ignition system problems - Check ignition system and replace faulty parts.
Damaged gaskets - Change gaskets.
Powerhead components are damaged - Replace defective components.
Incorrect propeller selection - Install correct propeller.
Damaged or bent propeller - Replace propeller.
Incorrect outboard motor mounting height - Check the outboard engine mounting height.
Improper trim angle - Make the correct trim angle adjustment.
| High fuel consumption |
Incorrect adjustment of carburetor main jet - Adjust main jet as required.
Faulty or loose spark plug - Replace or tighten spark plug.
Worn piston, rings, or sleeve - Replace defective parts.
| Motor vibrates excessively |
Propeller bent or damaged - Replace propeller.
Propeller shaft malfunction - Have propeller shaft replaced.
Weeds wraped around propeller - Clean the propeller.
Motor mounting bolt is loose - Tighten the bolt as required.
Steering pivot is loose or damaged Tighten correctly or replace.
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