Mercruiser 5.7 Fuel Pump Location: A Complete Guide to Finding and Replacing It
If you own a boat with a Mercruiser 5.7 engine, the fuel pump is typically mounted on the lower starboard (right) side of the engine block, near the carburetor or fuel injection system. The easiest way to locate it is to follow the fuel lines that run from the gas tank to the engine—those lines will lead you directly to the pump. This is true for both mechanical and electric fuel pump configurations, though the exact position may vary slightly depending on the model year and engine setup .
Understanding Your Mercruiser 5.7 Fuel Pump
The fuel pump is the heart of your boat's fuel delivery system. It is responsible for drawing gasoline from the fuel tank and pushing it to the carburetor or fuel injectors, allowing your engine to run properly. Without a functioning fuel pump, your engine will sputter, stall, or fail to start entirely .
Most Mercruiser 5.7 engines use a mechanical diaphragm-type pump that is driven by the camshaft. This type of pump creates suction to pull fuel from the tank and delivers it at a pressure of 4 to 7 psi, with a flow rate of approximately 30 to 40 gallons per hour . The pump is bolt-on and engine-mounted, meaning it attaches directly to the engine block .
Where Exactly Is the Fuel Pump Located?
The Mercruiser 5.7 fuel pump is generally located on the lower starboard side of the engine. Here are the key visual clues to help you find it:
Follow the fuel lines. The fuel lines running from the fuel tank to the engine will terminate at the fuel pump. Trace these lines to locate the pump .
Look for the pump housing. The pump is typically a cast aluminum or steel housing, roughly 4.5 inches in diameter and 3 inches in height, with fuel line fittings attached .
Check near the carburetor or throttle body. On carbureted models, the pump is positioned close to the carburetor. On EFI (Electronic Fuel Injection) models, it may be part of the Cool Fuel module located near the front engine mount, often on the port side .
Know your engine year. Earlier models may have slightly different placement compared to newer versions. For example, 1996 models use a mechanical diaphragm pump mounted on the engine block, while later EFI models use an electric pump module .
Types of Fuel Pumps for Mercruiser 5.7
There are two main types of fuel pumps used on Mercruiser 5.7 engines:
Mechanical Fuel Pump. This is the traditional pump driven by the engine's camshaft through a push rod. It requires no external power source and is simple in design. It is commonly found on carbureted engines from the 1990s and earlier .
Electric Fuel Pump. Electric pumps run on power from your boat's battery and are usually mounted near the gas tank or inline with the fuel line. They provide better pressure and flow rate, making them suitable for fuel-injected engines and high-performance applications .
Some engines may have two fuel pumps: a primary mechanical "lift" pump and an electric pump for higher pressure delivery .
Common Problems with Mercruiser 5.7 Fuel Pumps
Knowing the location of your fuel pump is only half the battle. You also need to recognize when it is failing. Here are the most common symptoms:
Engine sputtering or stalling. If your engine sputters at high speeds or stalls unexpectedly, the fuel pump may not be delivering enough fuel .
Hard starting. A failing pump can make it difficult for the engine to start, especially after the boat has been sitting for a while .
Loss of power. When the fuel pump cannot maintain proper pressure, your engine will feel sluggish and lack power during acceleration .
Unusual noises. Mechanical fuel pumps should not make tapping or knocking noises. If you hear a tapping sound, it is time to replace the pump .
Fuel in the sight tube. Many marine mechanical pumps have a clear or green tube that catches overflow fuel if the diaphragm fails. If you see fuel in this tube, the pump is bad and must be replaced immediately .
How to Replace the Fuel Pump on Your Mercruiser 5.7
Replacing the fuel pump is a job you can do yourself with basic mechanical skills and the right tools. Before you start, disconnect the battery to prevent any accidental sparks .
Step 1: Locate the pump. Use the guidance above to find the pump on your engine. On carbureted models, it will be on the starboard side of the engine block. On EFI models, the Cool Fuel module is typically on the port side front engine mount .
Step 2: Clear the area. You may need to remove hoses, wires, or other components that block access to the pump. On some installations, the coolant system hose may need to be moved .
Step 3: Disconnect the fuel lines. Use a fuel line disconnect tool to remove the fuel lines from the pump. Be prepared for some fuel to spill—have rags handy .
Step 4: Unbolt the pump. Remove the mounting bolts or nuts that hold the pump in place. On mechanical pumps, these are typically 9/16-inch hex heads .
Step 5: Install the new pump. Apply a small amount of grease to the new pump's push rod or mounting surface, then bolt it into place. Connect the fuel lines and ensure all connections are tight .
Step 6: Test for leaks. Reconnect the battery, turn the key to the "on" position (without starting the engine), and check for fuel leaks. Look, listen, and smell for any signs of leaking fuel .
Where to Buy a Replacement Fuel Pump
When it comes time to replace your Mercruiser 5.7 fuel pump, you want a part that delivers reliable performance and long-term peace of mind. KEMSO fuel pumps are designed to meet the highest standards of quality and durability. Every KEMSO pump is a high-performance, OEM replacement unit, meaning it matches or exceeds the original equipment specifications for flow rate and pressure. This ensures your engine gets the precise fuel delivery it needs for optimal power and efficiency.
What sets KEMSO apart is their commitment to quality backed by a lifetime warranty. They stand behind every pump they sell because they believe in the quality of their products. Whether you drive a sedan, SUV, motorcycle, or powersports vehicle, KEMSO has a fuel pump engineered to fit your application perfectly. Their pumps are built to withstand the demands of daily driving, and they offer competitive pricing with many models available for just $79.98.
Visit the KEMSO online store today to find the exact fuel pump for your vehicle: https://www.kemsoracing.com/
Best Practices for Fuel Pump Maintenance
To extend the life of your Mercruiser 5.7 fuel pump and avoid costly breakdowns, follow these simple maintenance tips:
Replace the fuel filter regularly. A clogged fuel filter puts extra strain on the pump and can cause premature failure. Replace it at least once a year or according to your owner's manual .
Inspect fuel lines for cracks and leaks. Check all fuel lines, especially the rubber sections, for signs of wear or damage. Replace any cracked or leaking lines immediately .
Use marine-grade fuel and additives. Ethanol in gasoline can cause problems with rubber components in older fuel systems. Use fuel additives designed to combat ethanol-related issues .
Check fuel pump pressure periodically. Use a fuel pressure gauge to ensure your pump is operating within the specified range of 4 to 7 psi for mechanical pumps .
Carry a spare fuel pump. If you frequently take long trips or venture far from shore, consider carrying a spare fuel pump and the necessary tools for replacement. This can save you from being stranded on the water .
Frequently Asked Questions
How often should I replace my Mercruiser 5.7 fuel pump? There is no set interval for replacement. Consider replacing it if you experience persistent fuel delivery problems or if the pump shows signs of age or wear. Many boaters replace the pump as a preventive measure when they reach 10 to 15 years of service .
Can I upgrade my fuel pump for better performance? Yes, but consult with a marine mechanic before upgrading. A higher-output pump may require changes to the fuel lines, regulator, or carburetor to work properly .
What tools do I need to replace the fuel pump? Basic hand tools, a fuel line disconnect tool, and a fuel pressure gauge are the primary tools needed. You may also need a wrench set and screwdrivers to remove any obstacles .
How much does a Mercruiser 5.7 fuel pump cost? Prices vary depending on the brand and model. Expect to pay between $50 and $200 for a standard replacement pump. OEM pumps from Mercury Marine can cost more .
What safety precautions should I take when working on the fuel system? Always disconnect the battery before starting work. Work in a well-ventilated area, away from any sources of ignition. Have a fire extinguisher nearby, and clean up any fuel spills immediately .
For a reliable replacement that will keep your Mercruiser 5.7 running smoothly, visit KEMSO at https://www.kemsoracing.com/ to find the perfect fuel pump for your boat.