Yamaha 40B - User Manual

Questions and Answers

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Jennifer KingAug 14, 2025
How to fix irregular idling or stalling in my Yamaha 40B Outboard Motor?
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  Juan RhodesAug 14, 2025
  If your Yamaha Outboard Motor idles irregularly or stalls, here's what you can check: * Inspect and replace fouled or incorrect spark plugs. * Check for obstructions in the fuel system. * Replace contaminated or stale fuel. * Clean or replace the fuel filter. * Make sure the air vent screw on the fuel tank is open, the choke knob is in home position, and the motor angle is at the normal operating position. * Also, ensure the fuel joint connection is correct and the battery lead is securely connected. If these steps don't resolve the issue, have a Yamaha dealer check the ignition parts, warning system, spark plug gap, ignition wiring, engine oil, thermostat, carburetor adjustments, or fuel pump.
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William JohnstonAug 19, 2025
How to troubleshoot a Yamaha Outboard Motor when the starter won't operate?
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  bishopjamieAug 19, 2025
  If the starter on your Yamaha Outboard Motor won't operate, consider the following: * Check the battery condition and use a battery of the recommended capacity if it's weak or low. * Ensure battery connections are tight and clean any corrosion from the terminals. * Inspect the fuse for the electric start circuit and replace it with the correct amperage after addressing any electric overload. * Shift to neutral, in case the shift lever is in gear. For faulty starter components, have your Yamaha Outboard Motor serviced by a Yamaha dealer.
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Mr. Adam VasquezAug 25, 2025
Why is my Yamaha Outboard Motor vibrating so much?
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  francisrobertAug 26, 2025
  Excessive vibration in your Yamaha Outboard Motor can stem from several causes: * A damaged propeller should be repaired or replaced. * Remove any weeds or foreign matter tangled on the propeller. * Ensure the motor mounting bolts are tightened. For a damaged propeller shaft or loose/damaged steering pivot, it's best to have your Yamaha Outboard Motor serviced by a Yamaha dealer.
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jay61Oct 29, 2025
Why won't my Yamaha Outboard Motor start, even though the starter is working?
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  Melinda BarkerOct 29, 2025
  If your Yamaha Outboard Motor's starter operates but the engine doesn't start, several factors could be at play: * The fuel tank might be empty, requiring you to fill it with clean, fresh fuel. * The fuel could be contaminated or stale; in this case, replace it with clean, fresh fuel. * A clogged fuel filter could be the culprit, so clean or replace it. * The starting procedure might be incorrect; refer to the "STARTING ENGINE" section for guidance. * Other potential issues include fuel pump malfunctions, fouled or incorrect spark plugs, incorrectly fitted spark plug caps, poor ignition wiring, faulty ignition parts, a detached engine stop switch lanyard, or damaged engine inner parts. For issues beyond fuel, spark plugs, and wiring, consider having your Yamaha Outboard Motor se...
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yharrisNov 3, 2025
What does it mean when the warning buzzer sounds on my Yamaha Outboard Motor?
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  Linda PrattNov 3, 2025
  If the warning buzzer sounds or the indicator lamp lights on your Yamaha Outboard Motor, it indicates a potential issue. You can check the following: * Inspect the water intake for any restrictions that might be clogging the cooling system. * Ensure the engine oil level is adequate and fill the oil tank with the specified engine oil if it's low. * Verify that the spark plug has the correct heat range and replace it if necessary. * Confirm that you are using the specified engine oil and replace it if not. * If the engine oil is contaminated or deteriorated, replace it with a fresh, specified type. * Also, ensure that the load on the boat is properly distributed to maintain an even plane. For other potential problems, such as a clogged oil filter, malfunctioning oil feed/injecti...
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Elizabeth DixonNov 8, 2025
What to do if my Yamaha 40B is losing power?
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  stephenwilsonNov 8, 2025
  If your Yamaha Outboard Motor is experiencing power loss, several factors could be responsible: * Check for a damaged propeller and have it repaired or replaced. * Ensure the propeller pitch and diameter are correct for optimal speed. * Adjust the trim angle for efficient operation. * Verify the motor is mounted at the correct height on the transom. * Address any activated warning systems by identifying and correcting the cause. * Clean the boat bottom to remove marine growth. * Inspect, clean, or replace fouled or incorrect spark plugs. * Remove any weeds or foreign matter tangled on the gear housing. * Check for obstructions in the fuel system and clean or replace the fuel filter if clogged. * Replace contaminated or stale fuel with clean, fresh fuel. * Also, inspe...

Yamaha 40B Specifications

General

Engine Type	2-Stroke
Max Output	40 hp
Full Throttle RPM Range	4500-5500 rpm
Fuel Induction System	Carburetor
Fuel System	Carburetor
Starting System	Manual or Electric
Ignition System	CDI
Fuel Type	Gasoline
Lubrication	Premix
Shaft Length	20"
Cooling System	Water Cooled
Fuel Tank Capacity	24 Liters (6.3 US Gal) - External