Changing The Mercruiser Fuel Fill Hose: A Step-By-Step Guide

Mercruiser fuel fill hoses are available at most boat supply stores, including West Marine and Boaters World. The replacement process involves removing the access hatch for the fuel tank, detaching the hose clamps, and twisting the hose to break it loose from the barb. It is recommended to replace the vent hose and fuel feed hoses at the same time, as they may be showing similar signs of aging. The process can be challenging, and it is advisable to have two people for certain steps.

Disconnect the battery and fuel supply valve

Disconnecting the battery and fuel supply valve is a crucial step when working on your Mercruiser engine. This step ensures your safety and prevents any accidental sparks that could lead to a fire. Here is a detailed guide on how to do it:

Turn Off the Battery:

Locate the battery switches and turn them off. If your boat has battery disconnect switches, use them to disconnect the batteries. This will cut the power supply to the engine, ensuring that no electrical current can cause sparks during your work.

Disconnect the Negative Terminals:

For added safety, it is recommended to disconnect the negative terminals of the batteries. Use appropriate tools to loosen the terminal clamps and detach the negative cables. Make sure to wrap the terminals with insulating material or tape to prevent accidental contact.

Locate the Fuel Supply Valve:

The fuel supply valve is usually located near the fuel tank or engine. It controls the flow of fuel from the tank to the engine. It is typically a lever or knob that can be turned or pushed to shut off the fuel supply.

Shut Off the Fuel Supply Valve:

Once you have located the fuel supply valve, turn it to the "off" position. This will stop the flow of fuel to the engine. Make sure the valve is securely closed to prevent any accidental fuel leaks during your maintenance work.

Ventilate the Work Area:

Before proceeding with any maintenance or repair work, ensure proper ventilation in the bilge and engine compartment. Set up a fan to circulate fresh air and blow away any fuel vapors that may have accumulated. This step is crucial to prevent the buildup of flammable fumes.

Absorbent Towels:

Place absorbent towels or rags underneath the work area to catch any spilled fuel. This will help contain any fuel leaks and make cleanup easier. It is important to have a sufficient number of towels or rags to absorb any accidental spills.

By following these steps, you will have successfully disconnected the battery and fuel supply valve on your Mercruiser engine. Remember to exercise caution and always work in a well-ventilated area when dealing with fuel systems.

Remove the fuel tank access hatch

To remove the fuel tank access hatch, follow these steps:

First, go to the cockpit area and locate the forward-most access hatch for the fuel tank. This hatch will usually be covered by a cover or hatch/cover over the fuel tank. Once located, use a flat-head screwdriver to remove the hatch and set it aside.

Now, you should see the fuel fill hose and a smaller vent hose attached to the tank. Before proceeding, it is recommended to place a piece of duct tape over the opening of the barb fitting to prevent any residue from entering the tank.

Next, use a flat-head screwdriver to remove the hose clamps securing the hoses. If the clamps are in good condition, you can reuse them, but if they are damaged or worn, it is advisable to replace them with new ones.

After removing the clamps, use channel locks to grip and twist the hoses to break them loose from the barb fittings. Then, pull the hoses off the barbs using a twisting and pulling motion. You may need to use the channel locks to get enough leverage. Once the hoses are removed, cover the openings of the barb fittings with duct tape to prevent any residue from entering the tank.

At this point, you should also remove the bench seat in the cabin to gain better access to the hoses. On most boats, the bench seat is held in place by deck screws, so use a Phillips-head screwdriver to remove the screws and set the bench seat aside.

Now, look for the fill hose, vent hose, and a green wire (which grounds the tank fill) in the aft-most portion of the cabin on the port side. Use a flat-head screwdriver to loosen the hose clamps securing the fill hose and vent hose. Re-tighten the clamps on a lower portion of the hoses to prevent them from falling into the hull.

Again, use channel locks to grip and twist the fill hose to break it loose from the metal fill barb. Once it's loose, remove the hose and loosen the hose clamps. You will also need to remove the small aluminum chain hanging from under the metal barb fitting. This chain is likely for a one-way valve in the fill.

Now, you are ready to pull the new hose through the access hatch in the cockpit. It is crucial to pull the hose from the cockpit and NOT from inside the cabin, as it is likely to get stuck. Tape the new hose to the old one securely, ensuring there is no gap between the edges of the hoses. Use duct tape to create a strong joint that will allow the hoses to pass smoothly through the deck.

With the joint taped, begin to pull the old and new hoses through the deck from the cockpit. This will likely require two people, with one person pushing from inside the cabin and the other pulling from the cockpit. The person inside the cabin should focus on pushing the hose down into the glassed box area under the deck.

Continue pulling the hose until you see the joint from the cockpit access hatch. If the hose gets stuck, back up and try again, using a twisting motion on both ends to keep it moving. Once the joint is visible, remove the duct tape and old hose, being careful not to cut into the new hose.

Finally, place two hose clamps on the new hose and push it onto the barb fitting in the fuel tank. You can use liquid sealant on the fitting for a better seal if desired. Tighten the hose clamps securely, and you're done!

Disconnect the hose clamps and vent hose

Disconnecting the hose clamps and vent hose is a crucial step in changing the fuel fill hose of your Mercruiser. Here is a detailed, step-by-step guide to help you through the process:

Firstly, locate the fuel tank by opening the forward-most access hatch in the cockpit area. You will find the fill hose and a smaller vent hose attached to the tank. Using a flat-head screwdriver, remove the two hose clamps on the fill hose. It is important to tighten these clamps further down the hose to prevent them from sliding around and accidentally falling off once removed.

Next, use channel locks to grip and twist the hose, breaking it loose from the barb. Continue twisting and pulling the hose to remove it from the barb. You may need to use some force during this step. Once the hose is removed, immediately cover the opening of the barb fitting with duct tape to prevent any residue from entering the tank.

Now, loosen and remove the hose clamps from the fill hose. Inspect the condition of the clamps, and if they appear to be in good shape, you can reuse them. However, if they show signs of wear and tear, it is advisable to replace them with new ones.

Moving to the cabin, locate the bench seat and remove it by unscrewing the deck screws holding it in place. The number of screws may vary depending on the model of your Mercruiser. Once the seat is removed, look into the aft-most portion of the cabin on the port side. Here, you will find the fill hose, a looped vent hose, and a green wire that grounds the tank fill.

Using a flat-head screwdriver, loosen the two hose clamps that secure the fill hose. To prevent them from falling into the hull, re-tighten them onto a lower portion of the hose, keeping them out of the way. Now, use channel locks to grip and twist the fill hose until it breaks loose from the metal fill barb. Once it is loose, remove the hose and then loosen and remove the hose clamps, being careful not to drop them into the hull.

At this point, you should see a small aluminum chain hanging from under the metal barb fitting. This chain is likely associated with a one-way valve in the fill system. Remember to note its position for reassembly.

Now, you are ready to pull out the old hose and feed the new one through. Tape the new hose to the end of the old one, ensuring a strong joint with no gaps between the hoses. This smooth transition will prevent the hoses from getting stuck during the feeding process.

With the taped joint in place, begin pulling the old and new hoses through the deck from the cockpit area. This step may require two people: one to push from inside the cabin and the other to pull from the cockpit. Remember to focus on pushing the hose down into the glassed box area. You may need to use some force and jab the hose with your arm to get it through.

Once the hose joint becomes visible under the hatch, carefully remove the duct tape and old hose, being careful not to cut or damage the new hose. Finally, place two hose clamps on the new hose, push it back a bit, and wiggle it onto the barb fitting. You can also apply a liquid sealant to the fitting for an extra layer of protection. Tighten the hose clamps securely, and you are done with this section!

Remember to take your time and work carefully, especially when dealing with fuel systems. Safety should always be a top priority.

Remove the bench seat in the cabin

To remove the bench seat in the cabin, follow these steps:

Locate the bench seat in the cabin. This seat is typically held in place by deck screws, but the number and type of screws may vary depending on the model and year of your boat. In the case of the 2003 model mentioned in the source, the bench seat is secured with six deck screws.

Gather the necessary tools. For this step, you will need a Phillips screwdriver to remove the screws holding the bench seat in place.

Place the cushion or cushions on the bench seat in a safe location. If possible, remove the cushion(s) and place them in a secure area, such as the middle of the v-berth, to ensure they do not get damaged or misplaced during the fuel fill hose replacement process.

Remove the screws using the Phillips screwdriver. Carefully set the screws aside in a safe place to ensure they are not lost during the process.

Gently lift and remove the bench seat from the cabin. With the screws removed, you can now carefully lift and take out the bench seat. Set it aside in a safe location, clearing the area for the next steps in the fuel fill hose replacement procedure.

By following these steps, you will successfully remove the bench seat in the cabin, providing access to the fuel fill hose and facilitating the replacement process.

Disconnect the vacuum hose from the fuel pump regulator

Disconnecting the vacuum hose from the fuel pump regulator is a crucial step in maintaining your Mercruiser engine. Here is a detailed, step-by-step guide to help you through the process:

Step 1: Locate the Vacuum Hose

The first step is to identify the vacuum hose that needs to be disconnected. It is connected to the fuel pressure regulator on one end and may be found laying in the bilge on the other end. This hose is responsible for maintaining proper fuel pressure and needs to be secured properly to prevent fuel starvation issues.

Step 2: Prepare the Work Area

Before beginning any work, it is important to take safety precautions. Make sure you have adequate ventilation in the work area and that there are no open flames or sparks nearby. Place absorbent towels or rags underneath the work area to catch any spilled fuel.

Step 3: Disconnect the Vacuum Hose

Using the appropriate tools, carefully disconnect the vacuum hose from the fuel pump regulator. This may require some force, but be gentle to avoid damaging any nearby components. It is recommended to have multiple rags ready to catch any fuel that may leak or spill during this process.

Step 4: Secure the Hose

Once the hose is disconnected, it is important to secure it properly to prevent it from falling off. You can use nylon wire ties with mounting screw holes to attach the hose to nearby engine parts. This will ensure that the hose does not fall off and block the fuel pressure regulator vacuum port.

Step 5: Clean the Hose and Regulator

Over time, oil mist and blow-by gases can collect within the plenum interior and wick down the vacuum hose, blocking the fuel pressure regulator. Therefore, it is essential to clean or replace the intake plenum annually, including all the vacuum hoses. You can run water and air through the hose to ensure it is clear of any debris or residue.

Step 6: Reattach the Hose

After cleaning, reattach the vacuum hose to the fuel pump regulator, ensuring a secure connection. You may need to apply a small amount of lubricant to the o-ring or gasket before reattaching to create a tight seal.

Step 7: Test the System

Finally, test the fuel system by running the engine and checking for any fuel leaks. Pay close attention to the fuel pressure regulator and vacuum hose connection to ensure there are no signs of leakage. If you notice any issues, re-inspect the connection and make any necessary adjustments.

Remember to consult a professional marine mechanic if you are unsure about any part of this process or if you encounter any significant problems.

Frequently asked questions