55278A5 – Diaphragm Kit – Mercury / MerCruiser (Fuel Pump)

The 55278A5 Mercury diaphragm is a genuine OEM replacement fuel pump diaphragm kit for Mercury, MerCruiser, Mariner, and Force marine engines. This diaphragm kit helps maintain proper fuel flow and pressure in your boat’s fuel pump assembly. Because it matches original factory specifications, it provides the sealing you need for reliable engine performance.

This kit contains the flexible diaphragm component that actuates with the fuel pump’s movement. Over time, diaphragms can harden, crack, or lose their flexibility. When that happens, fuel delivery can become inconsistent or weak. Installing the 55278A5 Mercury diaphragm restores smooth fuel pump operation and helps eliminate issues like stalling or poor throttle response.

Many marine mechanics and boat owners replace this part during routine maintenance or whenever a fuel pump rebuild is needed. It offers a cost-effective way to keep your fuel system operating correctly. Because this part fits a range of Mercury and MerCruiser applications, it works for both inboard sterndrives and some outboard motors using the same fuel pump design.

This diaphragm kit resists fuel, heat, and vibration, yet it must still be checked regularly for wear if your boat spends a lot of time on the water. Using a fresh OEM diaphragm helps you avoid unexpected issues and supports better engine start-up and mid-range performance.

Shop at Arizona Outboard Dismantlers to keep your outboard running strong and ready for the water. We focus on parts that help you maintain peak marine engine performance.