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Troubleshooting Why Your Yamaha Outboard Motor Stopped Working

Cowling Cover Being Lifted Off a Yamaha Outboard

If your Yamaha outboard motor stopped working, you may not know the cause or how to start troubleshooting. Fortunately, Yamaha outboard motor problems are usually due to one of several common issues and may not require a mechanic. In this Yamaha outboard troubleshooting guide, we’ll discuss how to troubleshoot a Yamaha outboard motor that stopped running.

How Do You Troubleshoot a Yamaha Outboard Motor?

First, check for the simplest potential issues.

  • Is there gas in the tank?
  • Is the tank vent open?
  • Is the kill switch properly attached?
  • Is the gear shift in the neutral position?
  • Does the propeller have any debris wrapped about it, or damage?

Try to start the engine both with and without using the choke. If this doesn’t work, try altering the throttle position. Finally, squeeze the primer bulb a few times to make sure the engine is primed up.

Reasons Your Yamaha Outboard Still Isn’t Working

Ok, so you’ve tried the quick solutions, but you still haven’t figured out why your Yamaha outboard motor stopped working. The next step is to do a thorough once-over of each system/engine part until the mystery is solved.

Propeller

If your engine is vibrating excessively, it may be indicative of propeller problems. You should have already checked the propeller for damage and debris, but it’s possible something else has gone wrong. If you’re still unable to start your outboard motor, check the propeller shaft for damage or cracks– these may not be immediately apparent, but could indicate a need for replacement. Next, use a wrench to tighten the steering pivot and mounting bolt if either is loose.

Fuel System

The fuel system is composed of the fuel pump, fuel filter, check valves, fuel hoses, fuel pump diaphragm, and injectors. Listen for the operation sound. If you can’t hear the system attempting to work, check for continuity between the fuse holder, fuse, fuel pump relay, and wiring harness. Repair or replace the defective part(s) if there is no continuity. If there is continuity, replace the electrical fuel pump. If you hear the operation sound, check each part of the fuel system individually.

First, inspect the fuel filters and look for clogs, cracks, kinks, or leaks in the hoses. Replace any parts with damage. Next, check the diaphragm for cracks or other signs of damage. Then, check the vapor separator needle valve for bends or signs of wear. The next step is to check the injectors for clogs and resistance. Then, check for poor connections.

Finally, note if there is any water in the fuel. Ethanol gasoline attracts water, which negatively impacts the combustibility of the fuel. This is especially likely if you haven’t used fuel additives or stabilizers. Water in the fuel may also cause a bad or failing fuel pump. If you find water in your fuel, you may want to check that the pump is in good condition.

You can perform a Yamaha outboard fuel pump test by removing the spark plug wire boot from the spark plug and then removing the spark plug with a plug socket and wrench. Attach a compression gauge into the spark plug socket. If you have an electric motor, you may need a second person to crank your engine over while you twist your throttle position open. Otherwise, you can push the throttle open with one hand and pull the rope start.

What are the Symptoms of a Bad Fuel Pump on an Outboard Motor?

The earliest sign of damage is rapid fuel use. You also may have experienced a bumpy ride or issues with acceleration before getting to this point. If you’ve experienced these problems, you can reference PartsVu’s guide to diagnosing (and preventing!) a bad fuel pump to determine your next steps.

If at any point in this process you discover a part that has cracked, clogged, or shown other signs of wear, it’s most likely preventing your engine from starting. Consult a repair manual for your engine model and year to determine the proper replacement part.

Ignition System

The ignition system is responsible for firing up the engine and keeping it running. Because checking this system may involve sparks and heat, keep flammable liquids away.

The first part of the ignition system to check is the spark plugs. Clean and adjust the spark plugs– they may need to be replaced.

Check the ignition spark with a spark gap tester. If you’ve got a good spark, make sure that the air gap is within specification. Adjust it if needed. If you have a good spark and the gap is within specification, the problem will likely not be found in the ignition system.

However, if you don’t have a good spark, salt buildup on the spark plug caps or ignition coil leads could be causing problems. You’ll also need to check both the spark plug caps and ignition coil leads for proper resistance. Replace degraded parts. When there is no salt buildup and both parts have proper resistance, check the ECM output peak voltage.

If your spark plugs don’t seem to be the issue, check that the electric oil pump and oil level sensor are in good condition. If so, check the reed valve for its condition.

Starting System

If you hear a clicking sound when you attempt to crank the engine, the starter solenoid may be to blame. Depending on the model, you may be able to replace only the solenoid, or you may have to replace the entire self-contained system.

If the start motor isn’t starting at all, you likely have an electrical issue on your hands. Disconnect the black (negative) cable, followed by the red (positive). You’ll then need to remove the battery from its housing. If the battery is damaged, replace it. However, some signs of wear may be fixed.

Corrosion can be scrubbed away with a wire-bristle brush. Any other buildup or residue can be removed with a mixture of water and baking soda at a ratio of 1 cup:1 tablespoon, respectively. If you use this mixture, be sure to thoroughly dry the battery immediately after. Finally, charge the battery and clean the connections. Then, reconnect the positive cable, followed by the negative. Use dielectric grease when reinstalling the connections.

If all is well with the battery, you’ll need to check if a fuse has blown. To check if a fuse has blown, use a screwdriver to remove the electrical cover of the motor. With pliers, carefully remove the fuse holder. If the center is broken, that means it’s blown. You’ll have to check the Yamaha outboard repair manual to determine the correct amperage needed to replace it. If none of this works, continue onto the other systems until the issue is resolved.

What is the Life Expectancy of a Yamaha Outboard?

Yamaha outboard engines have a strong reputation for reliability, and for good reason. Your outboard engine life expectancy, at minimum, is about 1,500 hours (or, 6-8 years for the average boater). However, a properly maintained outboard engine can last more than 4,000 hours! This means that your engine could last for 16-21 years before needing to be replaced.

This guide to troubleshooting why your Yamaha outboard motor stopped working addresses issues common to the majority of Yamaha outboard models. We recommend that you locate or download the repair manual for your specific engine for more information, and consult a certified mechanic over any uncertainties.

8 comments

Hi I have a 2023 Yamaha f300xcb the engine starts and runs fine the issue is when shifting to the neutral position the engine shuts off. The engine always starts back up. The engine has about 550 hours at this time.
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Yamaha Outboard Maintenance replied:
Hi Leondus,

It sounds like your 2023 Yamaha F300XCB is experiencing an issue where it shuts off when shifting into neutral. A few potential causes to check:

1. Neutral Safety Switch – If the switch is faulty or misaligned, the engine may think it’s in gear and shut off. 2. Idle Control or Throttle Position Sensor (TPS) – A malfunctioning TPS or idle control system could cause stalling when returning to neutral. 3. Shift Linkage Adjustment – If the shift linkage is slightly off, it may not be fully engaging neutral, triggering a stall. 4. ECU or Software Update – Yamaha occasionally releases firmware updates that can resolve performance issues—checking with a dealer might be a good idea. 5. Fuel or Air Issue – While less likely since it runs fine otherwise, clogged fuel injectors or a dirty idle air control valve could contribute to the problem. Since your engine is relatively new and still under warranty, we highly recommend having it checked by an authorized Yamaha dealer or technician for a proper diagnosis. Let us know if we can assist in any way!

Best, Markine

Leondus leblanc,

My brother has a 2018 Yamaha F50 outboard motor with fuel injection. When you trim it up for a little bit with it off and then trim back down it acts like it’s not getting fuel to restart. When you get it start and run it’s fine but doesn’t want to idle real good after you trim it down. We checked the fuel filter and it’s fine,don’t believe it’s the fuel pump because it runs great when you open it up. Any help would be very appreciated! Thanks!
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Yamaha Outboard Maintenance replied:
Hi, Carroll Rhodes

It sounds like your brother’s 2018 Yamaha F50 is experiencing a fuel delivery or venting issue when trimming the motor. A few things to check:

1. Fuel Line and Venting – Make sure the fuel tank vent is open and not creating a vacuum that restricts fuel flow. Also, inspect the fuel lines for kinks or air leaks. 2. Air in the Fuel System – Trimming the engine up can sometimes cause air pockets in the fuel lines. Try priming the fuel bulb a few times before restarting. 3. Fuel Rail Pressure – Since it runs fine at higher speeds but struggles at idle, check the fuel pressure regulator and injectors to ensure proper fuel delivery. 4. Idle Air Control Valve (IACV) – If the engine struggles to idle after trimming, the IAC valve may be sticking or need cleaning. 5. Battery and Electrical Connections – Ensure strong voltage to the fuel injection system, as weak power can affect starting and idling. Since we’re not Yamaha Direct or certified mechanics, we recommend having the motor checked by a qualified Yamaha technician for a more precise diagnosis. Hope this helps, and let us know if you need anything else!

Best, Markine

Carroll Rhodes,

I have a 2015 yamaha f70. I had a bad fuel tank and replaced it with a external 6 gallon tank. I have issues with the motor not starting unless i pull out a spark plug. Then i put the plug in and it runs just fine just a little bit of a sputter at idle. If i try to start the next day i have to repeat the process. Any clue on what the problem is.
Thanks
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Yamaha Outboard Maintenance replied:
Hi Doug,

It sounds like you’re dealing with a fuel or ignition-related issue on your 2015 Yamaha F70. Since the motor starts after removing and reinstalling a spark plug, a few possible causes could be:

Excess fuel or flooding – Check if fuel is leaking into the cylinders when the engine is off. * Spark plug fouling – If the plug is wet or carbon-coated, it may indicate rich fuel mixture or ignition issues. * Air in the fuel line – Since you switched to an external tank, ensure the fuel lines and primer bulb are properly sealed and functioning. * Compression or valve issue – Less likely, but worth considering if the problem persists. Since we’re not Yamaha Direct or certified mechanics, we strongly recommend having your motor inspected by a qualified Yamaha technician. They can properly diagnose and resolve the issue to keep your engine running smoothly. Let us know if we can help in any other way!

Best, Markine

Doug Kunreuther,

I just purchased a 300hp outboard. It has 50 hr on it. Im have trouble trimming all the way down. One of the metal rods will not go down to let the motor trim all the way down. What should i do.
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Yamaha Outboard Maintenance replied:
Hi Jason,

It sounds like you’re dealing with a stuck trim/tilt rod, which can happen due to air in the hydraulic system, debris, or a mechanical issue. Here are a few things you can try:

1. Check for Obstructions – Inspect the trim rods and surrounding area for any debris or corrosion that might be preventing movement. 2. Manually Release Pressure – Locate the manual relief valve (usually on the trim unit) and carefully open it slightly to see if the motor will lower under its own weight. 3. Cycle the Trim Up & Down – If the motor moves slightly, try cycling the trim up and down multiple times to bleed any air out of the system. 4. Check Hydraulic Fluid – Low or contaminated fluid can cause issues. Make sure the trim reservoir is filled to the correct level. 5. Inspect for Damage – If one rod is stuck while the other moves, there may be a bent rod or internal hydraulic issue.

If none of these steps resolve the problem, you may need to have a technician inspect the trim system for potential hydraulic or mechanical failures. Let us know if you need further assistance!

Best, Markine

Jason lawlor,

Hello Joe
I have a 70 Beto in good nick, I took it out yesterday and was running fine for about 10 mins at high speed then slowed down and conked out.
I realised the primer bulb was slack so pumped it and off we went again and the same problem occurred. Not wanting to travel any further we returned to ramp cautiously having to pump the primer bulb continuously to prevent stopping.
Once home I removed cowling and noticed fuel filter/separator bulb was extremely loose, I tightened it up and ran it no problem but obviously not under load. Do you think this could’ve been the problem? And should I put it back in water or take it to a mechanic first?
Thanks Gaz


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Yamaha Outboard Maintenance replied:
Hi Gaz,

It sounds like the issue could definitely be related to the loose fuel filter/separator bulb. When the primer bulb is slack or the fuel system isn’t pressurized properly, it can cause fuel starvation, which would explain why your engine conked out after a short period of time. Pumping the primer bulb likely helped because it temporarily restored fuel flow, but once that pressure was lost again, the engine would have stalled. Since you’ve tightened it up and the motor ran fine without load, that’s a good sign, but you should definitely test it under load again before heading out too far. It’s a good idea to keep a close eye on it, and if the issue reoccurs, I’d recommend taking it to a mechanic just to rule out any deeper issues, such as a clogged fuel line or pump problem. If the problem persists, getting a mechanic to check it out would be a safe move. Better to be cautious! Good luck! Let us know how it goes. Best, Markine D

Gary Ellis,

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