Replacing Your Outboard's Fuel Pump: A Step-By-Step Guide

If you're experiencing issues with your Force outboard motor, such as sputtering, misfiring, or increased fuel consumption, you may need to replace the fuel pump. Before replacing the fuel pump, it's important to troubleshoot and diagnose the issue correctly. This can be done by checking for common symptoms of a failing fuel pump, such as failed starts, inconsistent power, and increased fuel consumption. Additionally, you can perform tests on the fuel pump, such as checking for continuity and listening for pump priming. If you decide to replace the fuel pump, it is recommended to consult a repair manual or seek assistance from a qualified technician. Regular maintenance and the use of fuel additives and stabilizers can also help enhance the performance and longevity of your boat engine.

Diagnose fuel pump issues

Diagnosing fuel pump issues in an outboard motor can be challenging, and the process often involves eliminating other potential causes. Fuel pump problems can manifest in several ways, including:

• Sputtering or misfiring
• Inability to start or maintain an idle
• Losing power when throttling up
• Increased fuel consumption
• Additional heat
• Inconsistent power

• Check the Basics: Ensure you have enough fuel in the tank and inspect the electrical system for any signs of corrosion or damage. Check that all fuses are intact and the system is functioning normally. Inspect the fuel system components, including filters, screens, fuel lines, and connections. Ensure all seals are working correctly.
• Check for Continuity: Establish if there is uninterrupted fuel flow from the tank to the pump. You can do this by pumping the primer bulb until it builds up pressure. The fuel should travel from the tank to the pump, filling the outboard fuel filter.
• Listen for Pump Priming: Fuel pumps often fail unexpectedly. If your boat doesn't start, listen for the fuel pump priming. In a dual-pump system, both pumps will prime. Put the ignition in the "on" position and listen for a whirring sound from the outboard motor. If you don't hear the priming sound, the fuel pump may have failed or may not be receiving power.
• Test the One-Way Valves: These valves deliver fuel through the system, allowing it to move in one direction from the tank to the rest of the fuel system. They build up pressure to allow continuous fuel flow. To test, remove the fuel pump, attach a pressure gauge to the outlet valve, and block the inlet valve with your thumb. If the pressure releases, the inlet is allowing pressure escape, and the valves may need replacing.
• Examine the Diaphragm: The diaphragm is a rubber component inside the fuel pump that pushes the fuel through. Signs of a damaged diaphragm include stalling, leaking, or fuel escaping into the water. To test, you'll need bolts, washers, and a hose clamp. Clamp and tighten the pump, attach the fuel lines to the inlet and outlet, and prime the bulb. If you see fuel leaking through the hole at the rear of the fuel pump, the diaphragm needs replacement.
• Check the Sump Screen: Ensure there is enough fuel in the tank to be picked up and check the sump pickup screen for clogs. Blow air through the tank vent to ensure it is flowing freely. Inspect the fuel primer bulb for leaks and cracks.
• Inspect Connections and Hoses: Check all fuel connections and hoses for leaks or kinks. Loosen the fuel filter hose clamps and remove the filter. Blow through both ends to look for obstructions. If the filter is clear, reinstall it and tighten the clamps.
• Check the Pulse Hose: Loosen the clamp on the pulse hose, which connects to the intake manifold and fuel pump. Place a container underneath the hose and crank the engine several times. If there is a lack of fuel discharge, it could indicate a faulty diaphragm or fuel pump check valve.
• Use a Compression Gauge: Screw a compression gauge hose into the spark plug hole and twist the throttle position wide open. Pull the rope start or turn the starter to turn the engine over several times. Refer to your owner's manual for the correct PSI. If the compression falls below the specified level, it could be due to low pulse pressure, indicating a potential issue with the fuel pump.

Check for continuity

Checking for continuity is an important step in troubleshooting a faulty outboard fuel pump. This step ensures that fuel can flow smoothly from the tank to the pump, which is crucial for the pump's operation. Here's a detailed guide on checking for continuity:

Before checking for continuity, it is important to perform basic checks on the fuel system. Ensure that there is enough fuel in the tank and that the gauge is functioning correctly. Examine the electrical system for any signs of corrosion or buildup on connectors, and verify that all fuses are intact. Inspect the fuel system components, including filters, screens, fuel lines, and connections, ensuring that all seals are in working order.

Now, to check for continuity:

• Locate the primer bulb: Find the primer bulb, which is usually easily accessible. It is typically made of rubber and may be located near the fuel tank or engine.
• Pump the primer bulb: Start pumping the primer bulb gently and repeatedly. You may need to pump it several times to build up pressure in the fuel system.
• Feel for resistance: As you pump the primer bulb, pay attention to how it feels. It should become harder to pump as you build up pressure. If it feels soft or doesn't build pressure, it could indicate a blockage or issue with the fuel pump.
• Observe the fuel flow: Check if the fuel is flowing smoothly from the tank to the pump. There should be no interruptions or blockages along the way. You may need to refer to your outboard motor's manual to identify the specific fuel flow path for your model.
• Inspect the outboard fuel filter: Located just before the fuel pump, the outboard fuel filter should be full when the engine is running. If it is not full, it could indicate a problem with fuel flow or a clogged filter.
• Repeat the process: To confirm your findings, repeat the above steps several times. This helps ensure that your observations are consistent and not due to a temporary issue.

If you find that fuel is not flowing smoothly or that the outboard fuel filter is not filling up, it could indicate a problem with the fuel pump or a blockage in the fuel system. In such cases, further troubleshooting or professional assistance may be required.

Checking for continuity is a vital step in diagnosing issues with your outboard fuel pump. It helps identify whether fuel is flowing properly, which is essential for the pump's operation and the overall performance of your boat. By following the above steps, you can ensure that your fuel system is functioning correctly and take appropriate action if any issues are identified.

Listen for pump priming

If your boat doesn't start, stop and listen for the fuel pump priming. Fuel pumps often fail unexpectedly, so it's important to check whether they are functioning properly. The fuel pump engages for a few moments before the engine starts. In a dual-pump system, both pumps will prime.

To test whether the fuel pump is priming, put the ignition in the "on" position and listen for a whirring sound from the outboard motor. Repeat the process a few times. If the fuel pump has failed, you won't hear the priming sound.

If you're having trouble hearing the priming sound, it could be due to issues with the battery. Check the battery first and, depending on other symptoms, consider troubleshooting other systems. If you're missing the motorized sound, that could indicate the fuel pump is having issues.

It's also important to note that fuel pump issues are often related to electrical and fuel systems. If your fuel pump is not priming, you may want to confirm that it's receiving electrical power. You can do this by using a multimeter or voltage meter to check the electrical connections and determine if the correct amount of electrical current is reaching the fuel pump.

By listening for the pump priming, you can quickly identify whether the fuel pump is functioning properly and take appropriate action if it is not.

Test the one-way valves

Testing the one-way valves is a crucial step in diagnosing fuel pump issues in outboard motors. These valves play a critical role in ensuring fuel flows in only one direction, from the tank to the carburetor, building sufficient pressure for continuous fuel flow. Here's a detailed guide on how to test the one-way valves:

• Remove the Fuel Pump: Before beginning the test, detach the fuel pump from the engine. This step provides easier access to the valves and simplifies the testing process.
• Understand Valve Types: There are two types of one-way valves to consider: the inlet valve and the outlet valve. The inlet valve accepts the fuel flow from the tank, usually marked with an arrow pointing inward towards the centre of the pump. The outlet valve, on the other hand, moves the fuel to the rest of the system and may be indicated by an arrow pointing outward.
• Attach the Pressure Gauge: Obtain a pressure gauge to test the functionality of the valves. Affix the pressure gauge hose securely to the outlet valve. This setup will help you monitor any changes in pressure during the test.
• Seal the Inlet Valve: Using your thumb, firmly seal the inlet valve. By blocking the inlet, you can focus solely on the outlet and identify any potential issues with the valves.
• Pump the Pressure Gauge: With the pressure gauge attached to the outlet and the inlet sealed, pump the pressure gauge several times. This action simulates the flow of fuel and helps identify any valve malfunctions.
• Observe Pressure Release: If the pressure releases or drops, it is a clear indication that the inlet valve is faulty. A properly functioning inlet valve should only allow fuel to pass in one direction. If pressure escapes in the reverse direction, it means the valves are not working correctly and need replacement.
• Repeat for Each Valve Pair: Remember that each pump has at least one inlet and one outlet valve, but some pumps may have two outlets. Therefore, it is essential to perform this test on each set of valves to ensure comprehensive diagnosis.

By following these steps and carefully observing the pressure gauge, you can effectively test the one-way valves in your outboard fuel pump. This process will help you identify any malfunctions or improper fuel flow, which could be the reason your outboard motor is experiencing issues.

Examine the diaphragm

To examine the diaphragm, you must first gather some bolts, four washers, and a hose clamp. You will then need to:

Clamp and tighten the pump:

Use the bolts and washers to clamp and tighten the pump. The bolts should go through the holes that usually attach the fuel pump to the engine, with washers on either end. This step is designed to maximise pressure.

Attach the fuel lines:

Attach one fuel line to the inlet and another to the outlet, clamping them securely.

Prime the bulb:

Prime the bulb and watch the hole at the rear of the fuel pump, where you can see a portion of the diaphragm. If you notice fuel leaking through this hole, you must replace the diaphragm.

Signs of damage:

Some signs of diaphragm damage include stalling, leaking, or fuel escaping into the water.

Repair or replacement:

If the diaphragm is faulty, the fuel pump will need to be rebuilt or replaced. Note that repair kits are not available for all fuel pumps, in which case, the pump will need to be replaced.

Frequently asked questions