Sierra 18-7817 Fuel Pump Diaphragm Kit, Replaces OEM 21-857005A1, for Mercury Outboard

The Sierra 18-7817 Fuel Pump Diaphragm Kit is a rebuild kit for the fuel pump on Mercury outboard engines. It is built to meet or exceed the performance of the original equipment part it replaces, giving boat owners a reliable way to restore fuel pump function without replacing the entire pump assembly.

The kit centers on a diaphragm designed as a direct equivalent to OEM part 21-857005A1, along with a fiber washer (part 18-4261, OE 19643) used during reassembly. Installing a fresh diaphragm and washer addresses common fuel pump issues such as loss of prime, fuel leakage, or inconsistent fuel delivery that develop as the original diaphragm material ages and hardens from repeated exposure to fuel and heat in the engine compartment.

The kit is compact and lightweight, packaged at 7 x 6 x 1 inches and weighing 0.04 pounds, and is intended for the rear position of the fuel pump assembly. Sierra sources its parts to the same specifications used by original equipment engine manufacturers and boat builders, so the 18-7817 kit is intended as a drop-in equivalent for the fuel pump diaphragm it replaces on applicable Mercury outboard engines.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7817
• UPC: 030999323019
• Category: Mercury Outboard Fuel Pump Kit
• Kit Contents: Diaphragm; Fiber Washer (Part 18-4261, OE 19643)
• Position: Rear
• Package Dimensions: 7 x 6 x 1 inches
• Weight: 0.04 pounds
• Exterior Finish: Machined

Fitment

Designed for Mercury outboard engines.

Replaces (OEM)

• 21-857005A1

Frequently Asked Questions

What does the Sierra 18-7817 Fuel Pump Diaphragm Kit include? The 18-7817 kit includes a diaphragm and a fiber washer (part 18-4261, OE 19643) needed to rebuild the fuel pump.

What OEM part number does 18-7817 replace? Sierra 18-7817 replaces OEM part 21-857005A1.

What engines is this fuel pump kit for? This kit is designed for Mercury outboard engines that use the fuel pump diaphragm covered by OEM part 21-857005A1.

How much does the 18-7817 kit weigh? The Sierra 18-7817 Fuel Pump Diaphragm Kit weighs 0.04 pounds.

What are the package dimensions of this kit? The 18-7817 kit ships in a package measuring 7 x 6 x 1 inches.

Where does the diaphragm in this kit install on the fuel pump? The 18-7817 diaphragm is used in the rear position of the fuel pump assembly.

Is the Sierra 18-7817 kit genuine OEM or aftermarket? It is a Sierra-manufactured replacement kit engineered to meet or exceed the original equipment part it replaces, rather than a part sourced directly from the engine manufacturer.

Does the kit include a gasket or just the diaphragm? The 18-7817 kit includes the diaphragm along with a fiber washer (part 18-4261, OE 19643); it does not list a separate gasket.

What is the fiber washer part number included in this kit? The fiber washer included with the 18-7817 diaphragm kit is Sierra part 18-4261, cross-referenced to OE number 19643.

Will this kit stop a Mercury outboard fuel pump from losing prime or leaking? Installing the diaphragm and washer from the 18-7817 kit addresses fuel pump issues like lost prime and leakage that result from a worn original diaphragm.

Is Sierra 18-7817 the correct number to search for this fuel pump kit? Yes, 18-7817 is the manufacturer part number for this Sierra fuel pump diaphragm kit.