Ameer Randolph
If you're experiencing issues with your Mercury outboard fuel line, it may be time for a replacement. Before disconnecting the fuel line from the engine, it is important to inspect the type of fuel hose in your tank. The fuel hose type can be identified by its colour and printing. For instance, a soft grey hose with red print indicates a fuel hose that is likely to disintegrate and cause issues with your engine. To prevent this, it is recommended to remove and dispose of the hose, cutting it into small pieces. Additionally, when dealing with a B1-15 Gray w/Blue Print fuel line, it is advised to heat the end of the line with hot water before installation to prevent damage. For Mercury FourStroke outboards below 60hp, priming the fuel system involves connecting the fuel line to the engine and pumping the primer bulb until it's firm. However, for outboards with 75hp or greater, the onboard electric fuel pump will prime the system.
How to remove a Mercury outboard fuel line from the engine
| Characteristics | Values |
|---|---|
| Fuel hose colour | Grey with no blue printing |
| Fuel hose issues | Internal disintegration, blockage at connectors, and fuel filter/carb plugging |
| Fuel hose solution | Remove and cut into small pieces for disposal |
| Fuel hose replacement | From the tank to the engine |
| Fuel system priming | Pump the primer bulb until firm, then start the engine |
| Fuel system vent | Keep the vent on the tank cap open |
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What You'll Learn
Troubleshooting a faulty fuel hose
Identifying the Problem:
Before attempting any repairs or adjustments, it's crucial to understand the symptoms and identify the root cause of the problem. Some common signs of a faulty fuel hose or fuel system include engine stalling, running rich, sputtering, hesitating, vibrating, or difficulty starting the engine. These issues can be caused by a clogged fuel filter, faulty fuel pump, blockage in the fuel line, or even a faulty spark plug.
Inspecting the Fuel Hose:
Begin by inspecting the fuel hose from the tank to the engine. Check for any visible damage, leaks, or restrictions in the fuel line. Look for any discolouration or printing on the hose, as this can indicate potential issues. For example, Mercury has used fuel hoses with old hard grey and stamped lettering, soft grey with red print, and stiffer grey with blue print. The soft hose with red print is known to be problematic as the rubber liner disintegrates and plugs fuel filters and carbs.
Performing Fuel Pressure Testing:
Fuel pressure testing is a critical step in diagnosing fuel-related issues. Connect a fuel pressure gauge to the fuel rail and jumper hoses to the fuel injector and fuel pump. Slowly open the fuel pump and observe the gauge. If the pressure is below the recommended level, it could indicate a faulty fuel pump or a clogged fuel filter. Regular checks on fuel pressure can help identify issues before they cause severe engine damage.
Resolving the Issue:
Depending on the specific problem identified, here are some troubleshooting techniques:
- If the fuel hose is damaged, leaking, or restricted, replace it with a suitable high-quality fuel hose designed for Mercury outboards. Ensure the hose is the correct size and type for your engine, considering factors such as engine size and fuel pressure requirements.
- If the fuel filter is clogged, replace it with a new one. Regular replacement of fuel filters is essential to maintain optimal engine performance.
- If the fuel pump is faulty, check for any errors and consider replacing it.
- Ensure that the fuel line connection is secure and tight but avoid over-tightening, which can damage the connector.
- Use a fuel hose support or guide to keep the hose in place and prevent it from rubbing against metal or moving parts.
By following these steps and staying vigilant about regular maintenance, you can effectively troubleshoot and resolve issues related to a faulty fuel hose on your Mercury outboard engine. Remember to consult a professional mechanic or technician if you are unsure about any aspects of the troubleshooting and repair process.
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Priming your fuel system
To prime your fuel system, you need to purge the air from the fuel line so that your engine will start when you turn the key or pull the rope.
Mercury FourStroke outboards 60hp and below are equipped with a primer bulb, a rubber spheroid the approximate size and shape of a chicken egg, located in the fuel line between the fuel tank and the engine. First, connect the fuel line to the engine, if it is not already attached, then pump (squeeze) the bulb repeatedly until it’s firm. It usually only takes a few pumps. When the bulb is firm, the line is charged and you can start the engine.
If your Mercury FourStroke outboard is 75hp or greater, the onboard electric fuel pump will prime the fuel system for you.
You can also refer to your owner's manual for detailed instructions on how to prime your fuel system. If you need further assistance, consult your local Mercury Authorized Dealer.
- Keep your fuel tanks clean and check them periodically for water and sediment.
- Check your fuel filter often to prevent fuel contaminants from entering your engine.
- Avoid using fuel with more than 10% ethanol in your Mercury engine, as the metal, rubber, and plastic components are not designed to tolerate higher levels of ethanol.
- When preparing your boat for offseason or long-term storage, use fresh, preferably ethanol-free fuel treated with a marine-rated fuel stabilizer.
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Disconnecting the fuel line
Before beginning any work on your Mercury outboard, it is essential to have a basic understanding of the fuel system. The fuel line on your Mercury outboard is responsible for delivering fuel from the tank to the engine. It is usually made of rubber or a synthetic material and can deteriorate over time due to exposure to fuel and engine heat.
To begin disconnecting the fuel line, you will need to locate the fuel bulb, which is typically positioned in the fuel line between the fuel tank and the engine. Once you have found the bulb, you can proceed to disconnect the fuel line from the engine. This step may require some force, and it is normal for a small amount of fuel to squirt out during this process. If you are struggling to disconnect the line, you may consider applying a light coating of silicone grease to the O-ring, which should help make the process smoother.
After successfully disconnecting the fuel line, you will want to inspect it for any signs of damage or deterioration. Pay close attention to the inner lining of the hose, as some older Mercury fuel lines were known to have issues with the lining sucking closed or shedding loose, which could lead to problems with fuel flow. If your fuel line is in poor condition or shows signs of degradation, it is highly recommended to replace it with a new one.
Finally, when you are ready to reconnect the fuel line, there is a specific procedure to follow to prime the fuel system. This process ensures that air is purged from the fuel line, allowing for a smooth start-up. Simply connect the fuel line to the engine, if it is not already attached, and pump the bulb repeatedly until it becomes firm. This usually takes just a few pumps, and once the bulb is firm, your fuel line is charged and ready to go.
By following these steps, you can safely and effectively disconnect and maintain the fuel line on your Mercury outboard motor, ensuring optimal performance and longevity for your boat's fuel system.
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Mercury outboard fuel line replacement
Mercury outboard fuel lines are prone to damage due to the high levels of ethanol in modern fuels. It is important to regularly inspect your fuel line for any signs of deterioration, especially if it is an older model with a grey hose and red or orange print. If you notice any issues, it is recommended to replace the fuel line as soon as possible to avoid further problems.
To replace the fuel line on a Mercury outboard engine, you will first need to purchase a suitable replacement. You can find Mercury Fuel Line Assemblies available from various retailers, including T-H Marine Supplies and Amazon. Make sure the fuel line you choose is compatible with your specific Mercury engine model.
Before beginning the replacement process, ensure you have all the necessary tools and safety equipment. Work in a well-ventilated area and wear protective gear such as gloves and eye protection. It is also recommended to have a coffee cup of piping hot water on hand to make the installation of the new fuel line easier.
Start by carefully removing the old fuel line, taking note of how it is routed and connected. Disconnect the fuel line from the fuel tank and engine, and dispose of it properly. Cut the old fuel line into small pieces to prevent it from being used again, as it may be damaged or deteriorated.
Now, you can install the new Mercury Fuel Line Assembly. Follow the instructions provided with your purchased assembly, as well as any specific guidelines for your Mercury outboard model. Ensure the new fuel line is securely connected to both the fuel tank and the engine, and that all clamps and fittings are tight.
Finally, test your new fuel line by filling the fuel tank and checking for any leaks or issues. Refer to your engine's manual for specific recommendations and safety procedures. By following these steps and staying vigilant about fuel line maintenance, you can help ensure the reliable performance of your Mercury outboard engine.
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Fuel line maintenance
The fuel line is an essential component of your boat's engine, and proper maintenance is key to ensuring reliable performance and avoiding costly repairs. Here are some detailed instructions and tips for maintaining the fuel line on your Mercury outboard engine.
Inspecting and Replacing the Fuel Line
Before each boating season, it is important to inspect your fuel line for any signs of deterioration or damage. Look for the type of fuel hose used, as Mercury has sold hoses in the past that have been known to fall apart internally. Specifically, check for a grey hose without blue printing on it, as this type of hose has a rubber liner that can disintegrate and cause blockages in connectors, fuel filters, and carburetors. If you find this type of hose, it is recommended to remove and replace it immediately.
Additionally, inspect the fuel line between the bulb and the engine. If you have a grey line with red or orange print, it is advisable to replace it as a preventative measure, as these lines were not designed to carry the levels of ethanol in today's fuels.
Fuel Filter Maintenance
Fuel filters play a crucial role in preventing fuel contaminants from entering your engine. It is important to inspect and replace your fuel filter according to the maintenance schedule in your owner's manual, typically every 100 hours or annually. Most current Mercury Marine engines are equipped with a water-separating filter mounted on the engine, which helps protect your engine from water that enters the fuel system.
Consider installing a remote fuel filter to enhance water separation and increase filtering capacity. A remote filter can be located between the fuel tank and the engine and is especially beneficial for boats that travel far from their home port or go offshore for fishing. Remember to always keep spare filter elements on board in case of sudden clogging or unexpected issues.
Fuel Source and Tank Maintenance
To maintain the health of your fuel system, it is recommended to buy gas from known and trusted sources. Busy fuel docks or filling stations are more likely to provide fresh fuel. Keep your fuel tanks clean and check them regularly for water and sediment buildup. One method to check for water in your fuel tank is to siphon a small amount of fuel into a clear glass container, let it sit for about 30 minutes, and then look for a clear bubble or layer of water at the bottom.
Flushing and Running the Engine Dry
Flushing your outboard engine is an important part of maintenance. There are flushing adaptors available that allow you to use a hose for flushing if you don't have access to a large enough bucket. Running your engine dry at the end of the day or season is a common practice to prevent fuel from sitting in the carburetor for extended periods. However, some people choose to disconnect at only the tank end, which can cause the engine to starve for fuel and take longer to stop.
Additional Tips
- Always refer to your owner's manual for specific maintenance instructions and schedules.
- Consult with your local Mercury Authorized Dealer for expert advice and assistance.
- Keep your batteries properly maintained to ensure easy engine startup and proper functioning of electronic accessories.
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Frequently asked questions
To remove the fuel line from your Mercury outboard engine, you will need to disconnect the quick-disconnect fuel line. You may need to use a lot of force to do this, and it is normal for some fuel to squirt out when you do so.
The force may be due to a dry, old O ring. Applying a light coating of silicone grease that won't swell the O-ring can help with this.
There are three types of lettering on Mercury fuel hoses. The soft grey hose with red print is the "junk hose" that tends to disintegrate and should be removed and replaced. The other two types are the old hard grey with stamped lettering and the stiffer grey with blue print.
Always keep a cup of piping hot water on hand. Put the end of the line into the water for 20-30 seconds, shake the water from the line, and then install the new line. This will reduce the odds of damaging the brand-new line.
