Replacing Boat Fuel Lines: A Step-By-Step Guide

Fuel lines are an essential component of a boat's fuel system, delivering fuel from the tank to the engine. However, over time, they can degrade and become brittle, cracked, or clogged, leading to potential fuel leaks and engine problems. Replacing fuel lines is a maintenance task that boat owners may need to undertake to ensure the vessel's safety and performance. This process involves removing the old lines, inspecting and cleaning the fuel system, and installing new, high-quality, ethanol-resistant fuel lines with appropriate clamps and fittings. While it can be a complex task, with many variables depending on the boat's make and model, it is crucial to follow best practices and manufacturer recommendations to avoid fuel system issues and potential safety hazards.

Check for fuel leaks and gas smell in the tank coffin or bilge

Checking for fuel leaks and gas smells in the tank coffin or bilge is an important step in replacing fuel lines on a boat. Here are some detailed instructions to guide you through the process:

• Before gassing up, open the access plate and smell for any gas odours. It is recommended to have one access plate at each end of the tank. If there is no gas smell, that's a good sign.
• After gassing up, repeat the smell test. Try not to fill the tank completely. If you smell gas this time, you may have porous fuel lines or a vent line. If there was no gas smell before gassing up, but there is one now, you may have a leaky sender flange.
• If you detect a gas smell, locate the leak. A visual inspection is a great place to start. Follow the fuel lines from the engine down to the fuel tank and look for anything suspect.
• If the leak is along the fuel hose, repair it before using the boat.
• If there is fuel in the bilge, it is likely coming from the fuel tank. A fuel filter may have rusted through, a fuel line may have a hole, or there could be a leak from the fuel sender or pick-ups on the fuel tank.
• To confirm a fuel tank leak, pressure test the tank. Close off all the ports on the tank, including the fill port, vent port, and pick-up tube ports. Use an inflatable pipe plug for the fill port and hose pinch pliers for the vent hose.
• Disconnect the fuel pick-up hose and attach it to an air pump. Pump up to 3 PSI and observe if there is any pressure loss. If there is, spray soapy water around the ports and hoses to identify the source of the leak.
• If there is air coming out of the vent, disconnect the hose and seal off the port. Check the fuel sender as well.
• If there is no air coming out of the identified ports but you are still losing air, there may be a hole in the fuel tank.
• If you suspect a fuel tank leak, consider your options for repair or replacement. Patching or rigging the tank may be possible, but for safety reasons, it is generally recommended to replace the tank, especially for offshore or long-distance boating.
• If you choose to continue boating before replacing the tank, use a remote fuel tank as a temporary solution. Place a large remote fuel tank (20-30 gallons) in the back of the boat and hook it up. However, this option may be challenging if you have limited space in the transom area.
• Remember, smelling fuel on a boat can quickly become a serious issue. Always prioritise safety and consult a professional if you are unsure about any aspects of the process.

Pay extra attention to the line from the filter to the primer bulb

When replacing the fuel lines on a boat, it is important to pay close attention to the line from the filter to the primer bulb. This section of the fuel line is often exposed to UV rays, especially in the motor well, which can cause it to age more quickly than other parts of the line. Therefore, it is recommended to regularly inspect this part of the line for any signs of deterioration or stiffness.

To replace the fuel line from the filter to the primer bulb, start by removing the old line. Cut the line at the filter and the primer bulb, taking care not to damage any nearby components. It is important to ensure that the new fuel line is the correct size; typically, the hose size for the run from the tank to the primer bulb is 3/8 inch. When installing the new line, use a genuine OEM primer bulb as these are generally better made and more reliable than aftermarket alternatives. Lubricate the fittings and the hose with 2-cycle oil to reduce friction and make the installation process easier.

Additionally, when working with fuel lines, it is important to be cautious and use the proper clamps to avoid any potential fuel leaks. It is also recommended to replace the primer bulb if it is old, as they typically do not last as long as the fuel lines. By following these steps and paying extra attention to the line from the filter to the primer bulb, you can help ensure the safety and proper functioning of your boat's fuel system.

Use a genuine Yamaha bulb as non-OEM parts are not good substitutes

When replacing the fuel lines on a boat, it is important to pay attention to the primer bulb. While the fuel lines themselves are susceptible to damage from UV rays, the primer bulbs tend to deteriorate faster. Therefore, it is recommended to replace the primer bulb along with the fuel lines.

In particular, if you are using a Yamaha outboard motor, it is advised to use a genuine Yamaha primer bulb. While non-OEM parts might be cheaper, they are often poorly made and can cause issues. The Yamaha primer bulbs are designed specifically for their outboard motors and ensure a proper fit and optimal performance. The OEM bulbs are generally better made and worth the extra cost to avoid potential problems down the line.

When purchasing a Yamaha primer bulb, make sure to get the correct size for your motor. The most common sizes are 5/16 inch and 3/8 inch. The bulb should fit snugly onto the fuel line without being too tight. It is also important to consider the length of the fuel line you need, as it may be longer than you initially estimate due to the routing.

Additionally, when replacing the fuel lines, keep in mind that the lines from the tank to the primer bulb are typically 3/8 inch, while the lines from the primer bulb into the engine are usually 5/16 inch. This information will help ensure you get the correct parts for your Yamaha outboard motor and facilitate a smooth replacement process.

Check fill and vent hoses carefully for signs of deterioration

When replacing the fuel lines on a boat, it is important to carefully check the fill and vent hoses for signs of deterioration. This is because the fuel lines are crucial for the safe and efficient operation of the boat's engine, and any deterioration or damage to the hoses can lead to fuel leaks, which pose a safety hazard.

To inspect the fill and vent hoses for deterioration, start by locating the hoses. The fill hose is usually the largest hose connected to the fuel tank, while the vent hose is typically smaller in diameter and more flexible. Once you have identified the hoses, carefully examine them for any signs of cracking, brittleness, or degradation. Pay close attention to areas that are exposed to UV rays, as these sections tend to age quicker. Look for any signs of fuel leaks or a fuel smell, which could indicate that the hoses are not sealing properly.

If you notice any deterioration or damage to the fill and vent hoses, it is important to replace them as soon as possible. Replacing the hoses can help prevent fuel leaks and ensure the proper functioning of your boat's engine. When replacing the hoses, use high-quality, marine-grade fuel line hoses that are ethanol-resistant. Additionally, make sure to use the correct hose sizes for your specific boat and engine.

By regularly inspecting and maintaining the fuel lines, including the fill and vent hoses, you can help ensure the safe and reliable operation of your boat, preventing potential fuel leaks and engine problems.

Use a heat gun or dish soap and water to soften the hose when attaching to the tank

When replacing the fuel lines on a boat, you may need to soften the hose to attach it to the tank. This can be achieved using a heat gun or by soaking the hose in hot water. Here's a detailed guide on both methods:

Using a Heat Gun:

• Set the heat gun to a low or medium setting. Heat guns can generate temperatures between 100 °C and 550 °C (200-1000 °F), but a lower temperature is sufficient for softening the hose.
• Place the boat hose on a clean, heat-resistant surface or mat. Ensure that the work area is clear of any flammable materials.
• Turn on the heat gun and position it 2-3 inches away from the hose. Keep it moving along the length of the hose to avoid overheating any single spot.
• The heat will soften the rubber, making it more pliable. Continue applying heat until the hose is flexible enough to attach to the tank.
• Once finished, turn off the heat gun and allow it to cool down before storing it.

Using Dish Soap and Water:

• Boil some water and pour it into an unbreakable, insulated mug.
• Submerge the end of the hose that will attach to the tank into the hot water. Let it soak for several minutes to soften the rubber.
• While the hose is soaking, lubricate the end of the tank fitting with dish soap. This will make it easier to attach the hose.
• Remove the hose from the water and use a wooden dowel to widen the hose end. Push the dowel into the heated end to stretch it out.
• Pull out the dowel and push the soaped-up fitting into the hose end. Apply firm, even pressure until the fitting is fully seated.
• Fasten the screws tightly to secure the connection.

By using either of these methods, you will be able to soften the hose and create a secure, leak-free connection between the hose and the tank when replacing the fuel lines on your boat.

Frequently asked questions