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 provides a reliable replacement for specific Mercury and Mariner outboard engines. It is designed to restore original fuel system performance and efficiency.

This kit fits Mercury Mariner 70-90 HP (3-cylinder) and 100-115 HP (4-cylinder) models manufactured between 1983 and 1993. It directly replaces multiple OEM part numbers, ensuring wide compatibility for the specified engine range.

• Product Type: Fuel Pump Diaphragm Kit
• Installation Method: Direct replacement
• Fuel Compatibility: Designed for use with gasoline

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

This kit includes all necessary diaphragms and gaskets for a complete rebuild. Verify contents against your service manual before installation.

Installation Guide

1. Safety First: Disconnect the battery and ensure the engine is cool. Work in a well-ventilated area away from sparks or open flames.
2. Locate Fuel Pump: Identify the fuel pump on the engine block.
3. Disconnect Fuel Lines: Carefully disconnect the inlet and outlet fuel lines. Have a rag ready to catch any residual fuel.
4. Remove Pump: Unbolt the fuel pump from the engine. Note the orientation of bolts and fittings.
5. Disassemble Pump: Carefully disassemble the pump housing to access the old diaphragm and gaskets.
6. Install New Components: Replace the old diaphragm and gaskets with the new parts from the kit, ensuring correct alignment.
7. Reassemble Pump: Securely reassemble the pump housing.
8. Reinstall Pump: Mount the fuel pump back onto the engine and tighten the mounting bolts to the manufacturer's specifications.
9. Reconnect Lines: Re-attach the fuel lines securely to the pump.
10. Final Check: Reconnect the battery. Prime the fuel system and check thoroughly for any leaks before starting the engine.

Troubleshooting & FAQ

How do I confirm this kit fits my engine?
This kit is designed for Mercury/Mariner 3-cylinder (70-90 HP, 1983–1993) and 4-cylinder (100-115 HP, 1988–1993) models. To guarantee fitment, check the compatible engine chart and cross-reference your original part number with those listed (42909A1, 42909A2, 42909A3, 42909A4). Pay close attention to notes regarding the 90-degree oil check valve or fuel pump body color.

What are common symptoms of a failing fuel pump diaphragm?
A faulty diaphragm can cause engine hesitation, stalling at low speeds, difficulty starting, or a noticeable drop in overall performance. You may also observe fuel leaking from the pump's weep hole or housing seams.

How often should a fuel pump diaphragm be replaced?
There is no fixed replacement interval, but it is good practice to inspect the fuel pump during regular service. Replacement is recommended if you notice any signs of wear, fuel leaks, or performance degradation. Ethanol-blended fuels can sometimes accelerate wear on rubber components.

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.