Ameer Randolph
The Mercury 115 HP 4-stroke engine is a powerful and reliable motor that can be found on many boats. It is important to ensure that the engine is well-maintained and that the correct parts are used to ensure optimal performance and longevity. One of the key components of the engine is the fuel line, which transports fuel from the tank to the engine. So, what size fuel line is required for the Mercury 115 HP 4-stroke engine?
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What You'll Learn
Mercury 115 hp 4-stroke fuel line size is 3/8
The Mercury 115 hp 4-stroke fuel line size is 3/8". This size is specified in the manuals for several Mercury engines, including the Johnson 120 2-stroke and the 250 EFI. It is also commonly found on boats over 20 feet in length.
It's important to note that some sources recommend using a 5/16" fuel line for Mercury outboards with 50-90 horsepower. However, for the 115 hp 4-stroke engine, the recommended size is 3/8".
When choosing a fuel hose, ensure it is marked "SAE or USCG" approved to withstand the effects of ethanol. Mercury's silver fuel hose is a reliable option, but be aware of potential issues with the inner liner separating, causing restrictions.
Additionally, when installing the fuel hose, it is recommended to use genuine Mercury tie wraps with a curve to avoid leaks. The correct size for the primer bulb is 3/8", while the size out of the bulb should be 5/16" to ensure a secure grip on the barbs of the motor.
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5/16 is also suitable for Mercury 115 hp 4-stroke
A 5/16" fuel line is suitable for a Mercury 115 hp 4-stroke engine. This size is generally suitable for outboard engines up to 115 hp. A 5/16" fuel line is perfect for smaller outboards, allowing the proper amount of fuel to reach the engine without any problems.
The Mercury 115 hp engine is at the upper limit for using a 5/16" fuel line. Some sources suggest that a 3/8" fuel line is required for engines larger than 115 hp. This is because larger outboards require more fuel to run at higher RPMs, and a 5/16" fuel line can cause strain on the fuel pumps, potentially leading to premature failure or damage to the engine.
However, it is important to note that the Mercury 115 hp engine is designed to be durable and long-lasting, with a heavy-duty powerhead. Therefore, using a 5/16" fuel line may still be suitable for this specific engine, especially if the boat is on the smaller side, as the Mercury 115 hp engine is designed to power boats from 14' to 23' in single-engine applications.
Additionally, the connections at the fuel line hookup should be considered. The fuel line should fit tightly to avoid air leaks, which can cause problems with the engine's performance. If the 3/8" hose is too loose, it is recommended to switch to a 5/16" hose or use an adapter to step down from 3/8" to 5/16".
In summary, while the general recommendation for engines above 115 hp is to use a 3/8" fuel line, a 5/16" fuel line can also be suitable for a Mercury 115 hp 4-stroke engine, especially if the boat is on the smaller side and the connections are tight to avoid air leaks.
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Mercury EFI 250 Official Service Manual specifies a minimum of 5/16
The Mercury 115 EFI is a four-stroke outboard engine designed for low maintenance and easy maintenance. It is built with a heavy-duty powerhead, which is also used in the 200-hp Verado, and is designed to power a wide range of boats from 14' to 23' in a single-engine application and up to 28' in a twin installation. The engine is also appropriate for both single and twin installations in both freshwater and saltwater.
The Mercury EFI 250 Official Service Manual specifies a minimum of 5/16" for the fuel line size. This is the size recommended for a 50-90 horse outboard. However, some sources suggest that a 3/8" fuel line is needed for the 250 EFI engine, which is the size specified in the manual for the Johnson 120 2-stroke engine. It is important to refer to the official service manual and follow the recommended servicing procedures to ensure the correct fuel line size is used.
The Mercury 115 EFI engine also features SmartCraft Diagnostics, which provides real-time information on fuel management, boat speed, and potential issues. The Engine Guardian System monitors the engine and sends alerts or automatically adjusts the revs to protect against damage from low oil pressure or overheating. The engine also has a Maintenance-Free Valve Train, eliminating the need for costly and mandatory valve lash adjustments required in most four-stroke engines.
Overall, the Mercury 115 EFI is a reliable and durable engine, with a bulletproof powerhead and low-maintenance design, making it a popular choice for a range of boat applications.
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Boats over 20 ft typically have 3/8 ID fuel lines
When it comes to boats, ensuring the correct fuel line size is of utmost importance. Not only does it impact fuel efficiency, but also the safety of the vessel. Boats over 20 feet typically have 3/8" inner diameter (ID) fuel lines. This is because longer boats require larger fuel lines to accommodate greater fuel flow.
It is worth noting that there are different types of fuel hoses for different applications, and safety should always be a top priority. Hoses with US Coast Guard ratings of A1 and B1 are used for feeding fuel from the boat's fuel tank to the fuel filter bracket. The difference lies in their installation location: A1 hoses are used below the deck, while B1 hoses are used above the deck and do not have fire-resistant covering.
When connecting the fuel line to the boat, it is crucial to ensure a secure fit. If you encounter a loose connection, it is advisable to switch to a smaller hose size or install an adapter. For example, a 90 HP engine with a loose 3/8" hose should be changed to a 5/16" hose or fitted with an adapter to step down the line size.
Additionally, the Mercury 250 EFI engine requires a fuel line of at least 3/8" ID. The Johnson 120 2-stroke engine also specifies the same size in its manual. It is important to refer to the official manuals and seek expert advice when determining the appropriate fuel line size for your specific boat and engine setup.
By following these guidelines and staying informed about the latest updates and recommendations, you can ensure the optimal performance, safety, and longevity of your boat's fuel system.
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Mercury's silver fuel line has issues with the inner liner separating
Mercury's silver fuel line has been reported to have issues with the inner liner separating, causing a restriction. This issue was common in fuel lines used before 1982, when ethanol was introduced in gasoline. The ethanol causes the inner liner to react and separate, forming tumour-like growths on the inside of the line. This can lead to clogging in the connectors to the motor and tank, potentially causing fuel pump and carb issues.
To address this issue, Mercury developed a new hose with a liner on the inside to combat the negative effects of ethanol. This new design was intended to withstand the effects of ethanol and prevent separation. However, some users have still reported issues with the inner liner separating in the newer hoses, although it is unclear whether these issues are related to ethanol or other factors.
When replacing a fuel hose, it is recommended to use a fuel hose marked "SAE or USCG" approved. For Mercury engines, the fuel hose should be 3/8" into the bulb and 5/16" out of the bulb to prevent leaks. It is also recommended to use genuine Mercury tie wraps with the curve to secure the fuel hose.
It is important to regularly inspect the fuel hose for any signs of degradation or separation, especially if the boat was manufactured before 1982. If the inner liner is soft or separated, it is necessary to replace the fuel hose to avoid potential engine issues.
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Frequently asked questions
The recommended fuel line size for the Mercury 115 HP 4-stroke engine is 3/8".
Yes, a 5/16" fuel line can be used for the Mercury 115 HP 4-stroke engine. However, some sources recommend using a 3/8" fuel line for this engine. It is important to check your specific engine model's requirements.
Mercury's silver fuel line is recommended and should now be durable enough to withstand ethanol in gasoline. It is important to use a fuel hose marked "SAE or USCG" approved.
The fuel hose assembly includes a primer bulb and fuel connectors.
Officially, a primer bulb is not required for the Mercury 115 HP 4-stroke engine, but one can be installed. If the boat is used regularly, it is recommended to not have a primer bulb.
