Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4)

Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4)

This fuel pump diaphragm kit fits select Mercury and Mariner 2-Stroke outboards, including 70-90 HP 3-cylinder models (1983–1993) and 100-115 HP 4-cylinder models (1988–1993). It allows for a complete rebuild of the fuel pump assembly.

This kit is a direct replacement for Mercury OEM part numbers 42909A1, 42909A2, 42909A3, and 42909A4. It also cross-references with Sierra 18-7818-1, Mallory 9-37754, and GLM 40280.

• Product Type: Fuel Pump Diaphragm Rebuild Kit
• Installation: Direct replacement for original components
• Package Contents: Includes gaskets and diaphragms for a complete rebuild

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1 x Fuel Pump Diaphragm Kit (includes gaskets and diaphragms for a complete rebuild)

Installation Guide

1. Disconnect the battery and relieve any pressure in the fuel system before starting.
2. Remove the fuel pump from the engine assembly, carefully noting the orientation of fuel lines and fittings.
3. Disassemble the pump on a clean workbench, paying close attention to the order and orientation of diaphragms, gaskets, and covers.
4. Thoroughly clean all housing surfaces to remove any old gasket material or debris.
5. Inspect the pump housing for cracks, warping, or other damage before proceeding.
6. Install the new diaphragms and gaskets from the kit, ensuring they align correctly with the housing passages.
7. Reassemble the pump housing, tightening screws in a crisscross pattern to ensure an even seal and prevent leaks.
8. Mount the rebuilt fuel pump back onto the engine and securely reconnect all fuel lines.
9. Prime the fuel system according to the manufacturer's procedure and carefully check for any fuel leaks before starting the engine.

Troubleshooting & FAQ

How do I confirm this diaphragm kit fits my engine?
This kit is designed for specific Mercury/Mariner 3-cylinder (70-90 HP, 1983–1993) and 4-cylinder (100-115 HP, 1988–1993) models. Always cross-reference your engine's OEM part number with the numbers listed in our compatibility tables. Pay close attention to notes, as some models are only compatible if they have a 90-degree oil check valve or a specific (white) fuel pump body.

What are the signs of a failing fuel pump diaphragm?
Common signs include the engine bogging down at high speeds, difficulty starting, rough idling, or visible fuel leaks around the pump housing. A ruptured diaphragm can also allow fuel to leak into the engine crankcase, which can cause significant damage.

Is this kit all I need for a complete fuel pump rebuild?
Yes, this kit includes the essential gaskets and diaphragms required for a standard rebuild of the fuel pump. We recommend reviewing the product images to visually confirm all the components you require are included.

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.