Replacing A Fuel Pump In A Yamaha Boat Motor

If your Yamaha outboard motor is experiencing issues such as sputtering, misfiring, or increased fuel consumption, you may need to replace the fuel pump. In this guide, we will cover the steps to change the fuel pump on a Yamaha boat motor, including removing the old pump and installing a new one. We will also provide some tips on troubleshooting common fuel pump problems and share resources for purchasing replacement parts. By following these instructions, you can get your Yamaha boat motor running smoothly again and ensure a more enjoyable day on the water.

Disconnecting the battery cables

Before beginning, locate the battery. It is usually located in an easily accessible area of the boat. Once you have located the battery, gather the necessary tools, which may include a wrench or pliers.

The next step is to identify the positive and negative battery terminals. The positive terminal is usually marked with a "+" sign, and the cable is often red. The negative terminal is marked with a "-" sign, and the cable is typically black. It is important to be sure about the polarity to avoid any mishaps.

Loosen the nut or clamp connecting the positive cable to the battery terminal using your wrench or pliers. Do not let the wrench or pliers touch any part of the boat or engine while doing this, as it can cause sparks which may lead to an explosion. Once the nut or clamp is loose, carefully remove the cable from the terminal. You can place a piece of tape or a cap over the terminal to prevent accidental contact.

Repeat the same process for the negative cable, ensuring that your tools do not touch any part of the boat or engine. Again, cover the terminal with tape or a cap for safety.

With both cables disconnected, carefully move them away from the battery and secure them in a safe place, ensuring they do not touch any metal surfaces. This will prevent any accidental contact or short circuits.

It is important to note that you should never disconnect the negative cable first. Always start with the positive cable to prevent any potential sparks near the negative terminal, which could cause a short circuit.

By following these steps, you will have successfully disconnected the battery cables, ensuring a safe working environment as you proceed with changing the fuel pump on your Yamaha boat motor. Remember to exercise caution and use the appropriate tools throughout the process.

Removing the fuel pump

To remove the fuel pump from your Yamaha boat motor, start by disconnecting the cables from the battery. This is important as it prevents sparks from igniting any fuel vapors while you work on the fuel system.

Next, take a piece of duct tape and wrap it around each line on the three hoses connected to the fuel pump. This will help you remember where each hose connects. Label the tape with an indelible pen, marking where the hoses are connected: top, bottom, and cover plate. Now, disconnect the fuel hoses from the pump, capping the two fuel hoses with duct tape as you do so. Remove the vacuum hose that runs to the pump from the pump cover—this doesn't need to be capped.

Using a 1/4-inch socket, remove the bolt next to the pump cover nipple and the bolt diagonally across from it. You can now remove the pump from the engine block. Finally, use a razor blade, putty knife, or scraper to remove any remaining bits of the mounting gasket from the block.

Installing the new fuel pump

To install the new fuel pump, first, slip the two mounting bolts through the new pump, allowing you to fit the new gasket onto the bottom of the pump. The mounting bolts will hold the gasket in its proper alignment while you mount the new pump. Grab the pump and the gasket and set the pump in place on the engine block.

Thread the mounting bolts into the block and tighten them to 55 inch-pounds with a torque wrench. Reconnect the two fuel lines, using the tags as your guide, and reconnect the vacuum hose to the pump's cover. Wrap plastic wire ties around the lines to hold them in place on the pump.

Reinstall any parts you had to remove to gain access to the fuel pump, in the order in which you removed them. Finally, reconnect the cables to the battery.

Testing for a bad fuel pump

Before testing the fuel pump, it is important to check the rest of the fuel system for any cracks, leaks, or general signs of wear. Ensure that there is continuity between the fuel tank and the pump by pumping the primer bulb until it feels hard. The fuel should travel smoothly from the tank to the pump, and the outboard fuel filter should be full.

Next, with the engine off and the cowl cover removed, remove the spark plug wire boot and the spark plug itself. Attach a compression gauge to the spark plug hole, twist the throttle position wide open, and either pull the rope start or turn the starter over several times. If the PSI is low (generally under 30), it indicates a compression issue preventing the fuel pump from functioning properly.

The fuel pump's one-way valves and diaphragm are the most common sources of problems. To test the one-way valves, which deliver fuel from the tank to the carburetor, you will need to remove the fuel pump from the engine. Attach a pressure gauge hose to the outlet and seal the inlet with your thumb. Pump the pressure gauge a few times. If the pressure releases, it indicates that the inlet valve is faulty and allows pressure to escape in both directions.

If the one-way valves are functioning correctly, you can move on to testing the diaphragm, a rubber component inside the fuel pump that pushes the fuel through. Signs of a faulty diaphragm include stalling, leaking, or fuel escaping into the water. To test the diaphragm, clamp and tighten the pump using bolts and washers. Attach fuel lines to both the inlet and outlet, clamping them securely. Prime the bulb and watch the hole at the rear of the pump where the diaphragm is visible. If fuel is leaking through the hole, the diaphragm needs to be replaced.

Troubleshooting fuel pump issues

Identifying Symptoms:

When your Yamaha outboard motor is experiencing fuel pump issues, you may notice some telltale signs. Common symptoms include:

• Sputtering or misfiring: The engine may sputter, misfire, or even stall, indicating a potential issue with the fuel pump or a clogged fuel filter.
• Rapid fuel consumption: If you're burning through your fuel faster than usual, it could be a sign that the fuel pump is not functioning efficiently.
• Temperature rise: An increase in temperature on your gauge could be an indication of a failing fuel pump or other engine problems.
• Lack of the familiar motorized sound: When you start your engine, you should hear the fuel pump engaging. If this sound is absent, it could be due to a faulty fuel pump or battery issues.

Testing the Fuel Pump:

Before concluding that you have a faulty fuel pump, there are some tests you can perform:

• Check the battery: Ensure that the battery is in good condition and properly connected.
• Inspect the entire fuel system: Clogs or blockages in the fuel system can lead to similar symptoms. Check for any obstructions, cracks, or leaks in the fuel lines, fuel filter, and other components.
• Use a compression gauge: With the engine off, remove the spark plug and attach a compression gauge to the spark plug hole. Twist the throttle position wide open and pull the rope start or turn the starter. A low PSI (under 30) indicates a compression issue affecting the fuel pump's performance.
• Test the one-way valves: Remove the fuel pump from the engine and attach a pressure gauge hose to the outlet. Seal the inlet with your thumb and pump the pressure gauge. If the pressure releases, the valves are not functioning properly.
• Check the diaphragm: If your fuel pump has a diaphragm, you can test it by clamping and tightening the pump with bolts and washers. Attach fuel lines to the inlet and outlet, prime the bulb, and look for fuel leaks through the diaphragm.

Preventative Measures:

To avoid fuel pump issues, regular maintenance is key:

• Follow the manufacturer's recommendations for engine maintenance and replace the fuel pump as needed. Yamaha recommends replacing outboard fuel pumps every 3 years.
• Use fuel stabilizers to maintain fuel quality and protect the system during storage.
• Use fuel additives to counteract the negative effects of ethanol gasoline, which can lead to sludge formation and clogs.
• Refer to Yamaha's maintenance guides for a comprehensive checklist of parts to inspect for cracks, leaks, and wear.

Remember, fuel pump issues can be frustrating, but with the right troubleshooting techniques and preventative care, you can keep your Yamaha outboard motor running smoothly and efficiently.

Frequently asked questions