Replacing Yamaha F70 Fuel Pump: Step-By-Step Guide

Yamaha F70 fuel pumps are a common source of issues for boat owners, with many people taking to forums to discuss their problems and potential solutions. Some of the most common issues include the motor randomly dying at idle speed or while running, low fuel pressure, and fluctuating RPMs. There are several potential causes for these issues, including a faulty fuel pump, clogged fuel filter, or problems with the fuel lines or tank. In some cases, the issue may be as simple as a misaligned fuel bulb or a faulty anti-siphon valve. In other cases, it may be necessary to replace the fuel pump or other fuel system components. When replacing the fuel pump on a Yamaha F70, it is important to ensure that the new pump is compatible with the specific model and year of the outboard motor. Several aftermarket fuel pumps are available that are designed to meet or exceed OEM specifications and offer improved performance and durability. When replacing the fuel pump, it may also be advisable to replace other fuel system components, such as the fuel filter and fuel lines, to prevent future issues.

Diagnosing a faulty fuel pump

• Observe Engine Behaviour: Pay attention to how your engine behaves when you're out on the water. Common signs of a faulty fuel pump include random dying at idle speed or while running, loss of power, and rough idle. If you notice these issues, it could be an indication of a faulty fuel pump.
• Check the Fuel Bulb: A soft fuel bulb is often an indicator of a problem with the fuel pump. If you find that you need to pump the bulb frequently to keep the engine running, it's a sign that the fuel pump may not be functioning properly.
• Inspect the Fuel Lines: Kinks or pinholes in the fuel lines can cause fuel flow issues, leading to problems similar to those caused by a faulty fuel pump. Carefully inspect the fuel lines for any signs of damage or wear.
• Test with a Remote Tank: To isolate the issue, you can try running the engine on a remote fuel tank. If the engine runs without any problems, it's likely that the issue lies with your fuel lines or tank, and not the fuel pump.
• Check the Anti-Siphon Valve: A faulty anti-siphon valve can cause similar symptoms to a faulty fuel pump. Replacing the valve may resolve the issue.
• Inspect the Water/Fuel Separator: Ensure that the water/fuel separator is functioning properly and free of debris. A clogged separator can lead to fuel flow issues.
• Monitor Fuel Pressure: Install a fuel pressure gauge to monitor the fuel pressure. If the pressure drops off quickly, it could indicate a fuel system leak or a problem with the fuel pump.
• Check for Leaks: Leaks in the fuel system can cause a range of issues, including problems with the fuel pump. Carefully inspect all fuel lines, connections, and components for any signs of leaks.
• VST Filter and Pump: If you haven't replaced the VST (Vapor Separator Tank) filter and pump, they could be the source of the problem. Cleaning or replacing these components may resolve the issue.
• Fuel Injectors: Clogged or faulty fuel injectors can lead to fuel delivery issues. Have them inspected and cleaned or replaced if necessary.

Remember, safety should always be your top priority when working on your boat's engine. If you're unsure about any of these steps or the procedures involved, don't hesitate to consult a qualified marine mechanic.

Finding a replacement fuel pump

There are several replacement fuel pumps available for the Yamaha F70. When searching for a replacement fuel pump, it is important to consider the year and model of your Yamaha F70, as well as the specific part number of the fuel pump you need to replace.

Option 1: QFS OEM Marine/Outboard Fuel Pump Replacement

One option for a replacement fuel pump is the QFS OEM Marine/Outboard Fuel Pump Replacement. This fuel pump is designed to fit Yamaha 4-stroke F50/F60/F70/F75/F80/F90 models from 2005 to 2016. It is a direct replacement part that includes a fuel strainer and is designed for quick and easy drop-in installation. The pump features upgraded polymers, brushes, and commutators that guarantee consistent flow, amperage draw, and quiet operation. It is also compatible with modern ethanol-infused pump gasoline.

Option 2: RANSOTO 68V-24410-00-00 Fuel Pump

Another option for a replacement fuel pump is the RANSOTO 68V-24410-00-00 Fuel Pump. This fuel pump is compatible with 2000-UP Yamaha 4-stroke F75, F80, F90, F100, F115, and LF115 HP engines. It is designed to replace part numbers 880890T1, 880980A02, and 6D8-24410-00-00. This fuel pump is also compatible with modern ethanol-infused pump gasoline.

Option 3: KIPA Gas Fuel Pump

A third option for a replacement fuel pump is the KIPA Gas Fuel Pump. This fuel pump is compatible with 2000 Yamaha Four-Stroke Outboards F75, F80, F90, F100, F115, and LF115 HP engines. It is a direct replacement for OEM part number 68V-24410-00-00, 6D8-24410-00-00, 880890T1, and 880980A02. This fuel pump is designed for quiet operation and is compatible with modern ethanol-infused pump gasoline.

Option 4: HFP-385-OB2 QFS Fuel Pump

Finally, the HFP-385-OB2 QFS Fuel Pump is a comprehensive replacement option that includes a strainer/filter. This fuel pump is designed to meet or exceed OEM specifications and features upgrades that improve on the original design. It is compatible with a variety of applications, including Mercury Marine and Yamaha, and is backed by a lifetime warranty.

Installing a new fuel pump

Step 1: Prepare the Work Area

• Park your boat on a flat, level surface and engage the parking brake.
• Disconnect the negative terminal of the battery to prevent any accidental electrical shorts.
• Locate the fuel pump, which is usually found near the engine.

Step 2: Remove the Old Fuel Pump

• Place a container under the fuel lines to catch any spilled fuel.
• Loosen the clamps that secure the fuel lines to the pump and carefully remove the lines.
• Unbolt the fuel pump from the mounting bracket and set it aside.

Step 3: Install the New Fuel Pump

• Clean the mounting surface to ensure a proper seal.
• Position the new fuel pump in place and secure it with the mounting bolts. Ensure the pump is firmly in place.
• Reattach the fuel lines to the new pump, ensuring a tight and secure connection.

Step 4: Refill and Test

• Refill the fuel tank with fresh fuel.
• Reconnect the negative battery terminal.
• Start the engine and check for any leaks around the fuel pump and lines.
• Test the boat on the water to ensure the new fuel pump is functioning properly.

By following these steps, you can ensure a successful fuel pump replacement for your Yamaha F70. It is important to work carefully and consult a professional if you have any concerns during the process.

Testing the new fuel pump

• Start With the Basics: Check the fuel tank and gauge to ensure there is enough fuel and that the gauge is functioning correctly. Inspect the electrical system for any signs of corrosion or buildup on the connectors, and make sure all fuses are intact. Finally, examine the fuel system components, including filters, screens, fuel lines, and connections. Ensure that all seals are working correctly.
• Check for Continuity: Establish uninterrupted fuel flow by pumping the primer bulb until pressure builds up. Observe if the fuel travels from the tank to the pump, and the outboard fuel filter should fill up, indicating continuous flow.
• Listen for Pump Priming: If your boat doesn't start, pay attention to the sound of the fuel pump priming. Put the ignition in the "on" position and listen for a whirring sound from the outboard motor. Repeat this process a few times. If the fuel pump is not functioning, you won't hear the priming sound.
• Test the One-Way Valves: Detach the fuel pump and attach a pressure gauge to the outlet valve, blocking the inlet valve with your thumb. Pump the pressure gauge and then release your thumb. If the pressure escapes, it indicates that the inlet valve is faulty and needs replacement.
• Examine the Diaphragm: The diaphragm is a rubber component inside the fuel pump that pushes the fuel through. To test it, you'll need bolts, washers, and a hose clamp. Tighten the pump with bolts and washers at both ends, using the holes that attach the pump to the engine. Attach one fuel line to the inlet and the other to the outlet, securing them with clamps. Prime the bulb and observe the hole at the rear of the fuel pump where the diaphragm is located. If you see fuel leaking, the diaphragm needs to be replaced.
• Address Acceleration Issues: If your Yamaha F70 outboard motor is experiencing acceleration issues, it could be due to a spun propeller or problems with the fuel system. Inspect the fuel filter for signs of clogging or degradation, and clean or replace it if necessary. If you notice contaminants in the fuel filter, it may be time to replace the fuel lines as well.
• Proactive Maintenance: Regular maintenance can enhance the performance of your Yamaha F70 and reduce repair costs. Stay on top of routine maintenance as per the manufacturer's recommendations, and replace fuel pumps before they completely fail. Use fuel additives and stabilizers to improve fuel quality and protect the system during storage. Monitor your fuel lines for any signs of wear and tear, and tighten or replace hose clamps as needed. Keep all moving parts in the fuel pump properly lubricated to reduce friction and prolong their lifespan. Finally, clean your fuel filters regularly and replace them according to the manufacturer's guidelines.

Maintaining fuel pump health

Regular Fuel Filter Changes:

Contaminants in the fuel, such as dirt, debris, or water, can damage the pump over time. By regularly changing your fuel filter, you can prevent these contaminants from entering the pump, preserving its efficiency and longevity.

Maintain Fuel Levels:

Fuel acts as a coolant for the pump during operation. Consistently low fuel levels can lead to pump overheating and potential damage. Therefore, it is important to avoid frequent low fuel levels and always refuel your vehicle when necessary.

Use Clean Fuel:

Using clean, uncontaminated fuel is crucial for maintaining fuel pump health. Contaminated fuel can cause increased friction and premature wear on pump components. Always source your fuel from reputable suppliers and consider using fuel additives to maintain fuel quality.

Inspect and Maintain:

Regular inspections and maintenance checks are essential. Keep an eye on the fuel pump, fuel lines, and fuel gauge for any signs of damage or leaks. Listen for unusual noises, such as a loud whining sound, which could indicate a malfunctioning fuel pump.

Replace When Necessary:

Fuel pumps have a finite lifespan, and continuous use will eventually lead to decreased efficiency and potential failure. Be vigilant about the signs of a deteriorating fuel pump, such as engine sputtering, stalling, or decreased fuel efficiency. Consult your vehicle's manual for specific guidance on fuel pump maintenance and replacement intervals.

Test Fuel Pressure:

Testing your fuel pressure can help diagnose fuel pump issues. Start by installing a fuel pressure gauge and activating the fuel pump. Compare the pressure reading to the recommended specifications for your vehicle. If the pressure is below the recommended level, it may indicate a problem with the fuel pump or a clogged fuel filter.

Consult a Professional:

If you are unsure about any aspect of fuel pump maintenance or testing, don't hesitate to consult a professional mechanic. They can provide expert advice and ensure that your fuel pump is properly maintained or replaced if necessary.

Frequently asked questions