Sierra Marine Fuel Pump Kit for Johnson/Evinrude Outboards — 18-7800 replacement seals & check valves

The Sierra 18-7800 Marine Fuel Pump Kit is a complete replacement parts set engineered to restore proper fuel-pump function on compatible Johnson and Evinrude outboard motors.

This kit supplies the precision-molded check valves, O-rings, and gasket needed to rebuild or refresh an existing fuel pump assembly. All components are manufactured to meet or exceed original-equipment fit and tolerance so they mate cleanly with the pump body and deliver reliable sealing and valve action. The 18-7800 is designed as a direct, interchangeable service kit for several common OE part numbers used on older and current outboard engines.

Which parts are included in the kit and why they matter?

The Sierra 18-7800 kit contains two check valves, two different O-rings, and a fuel pump gasket—each part plays a specific role in controlling fuel flow and maintaining a leak-free seal. Replacing worn valves and seals prevents fuel leaks, improves pump efficiency, and helps maintain consistent performance under load.

• Two 18-7796 check valves — control one-way fuel flow inside the pump.
• One 18-7413 O-ring — seals a mating surface to prevent vapor or liquid leaks.
• One 18-7403 O-ring — second sealing point for reliable containment.
• One 18-0850 fuel pump gasket — replaces the pump-to-block seal to stop external leaks.

Will this kit fit my Johnson or Evinrude outboard?

The 18-7800 is intended as an interchangeable service kit for several OE numbers, so compatibility is broad across many Johnson and Evinrude pumps. Confirm fit by matching your engine’s pump model or cross-referenced OE part numbers before ordering.

• Interchanges with GLM 40850, Evinrude/Johnson 438616 and 433519, Mallory 9-37701.
• Works for pumps that use the same check valve and gasket layouts as those OE numbers.
• Check engine manual or remove pump cover to verify part shapes and dimensions.

How do these components affect pump performance and maintenance?

Worn or hardened O-rings and failing check valves commonly cause fuel leakage, vapor lock, or inconsistent fuel delivery. Replacing the internal seals and valves restores airtight pathways and proper one-way valve action, reducing fuel-system failures and improving starting and throttle response.

• New check valves restore correct pressure and flow direction inside the pump.
• Fresh O-rings and gasket renew sealing surfaces to eliminate leaks.
• Routine replacement during service intervals helps prevent roadside breakdowns.

What should I know about installation and service life?

Installation is straightforward for anyone familiar with small-engine fuel systems; basic disassembly of the pump housing and careful reassembly with correct torque settings are required. Use compatible lubricants on O-rings during installation, inspect mating surfaces for damage, and replace any additional worn components to ensure long-term reliability.

• Follow manufacturer torque and assembly guidance when reassembling the pump.
• Lightly lubricate O-rings with fuel-compatible grease for easier seating.
• Inspect pump diaphragm and housing for cracks—replace if deteriorated.

Who is this for: The Sierra 18-7800 kit is aimed at marine technicians, DIY boat owners, and service shops maintaining Johnson or Evinrude outboards that require OE-equivalent replacement valves and seals. It’s particularly useful when refreshing a fuel pump during routine maintenance or when troubleshooting fuel leaks and inconsistent engine operation. Verify compatibility with your engine’s pump model or the listed interchange numbers before purchase to ensure a proper match.