Fuel Pump Diaphragm Kit – Fits Mercury/Mariner/Force 30-275 HP

Fuel Pump Diaphragm Kit – Fits Mercury/Mariner/Force 30-275 HP

This fuel pump diaphragm kit is designed to restore performance to failing fuel pumps on a wide range of outboard motors. It provides a reliable solution for servicing square or triangular fuel pumps on select Mercury, Mariner, and Force engines.

This kit is a direct replacement for Mercury 857005A1 and 42990A10. It also replaces Sierra 18-7817, GLM 40290, and EMP 1399-39020.

• Compatible with gasoline fuel systems.
• Engineered for direct, hassle-free installation.
• Kit includes essential components for rebuilding one fuel pump.

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.

Confirm your engine model/year in the table below.

Mercury/Mariner Outboards

Force/Chrysler Outboards

Technical Specifications

Package Contents

• Fuel Pump Diaphragms
• Gaskets
• Check Valves
• 1 x Spring
• 1 x Cap
• Screws

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. Relieve Fuel Pressure: Carefully disconnect the fuel line to safely relieve any residual pressure in the system.
3. Remove Fuel Pump: Locate the fuel pump on the engine block. Remove the mounting bolts and detach the fuel lines to remove the pump assembly.
4. Disassemble Pump: Take note of the orientation of all components. Carefully remove the screws holding the pump housing together.
5. Replace Components: Remove the old diaphragm, gaskets, and check valves. Clean the housing surfaces thoroughly to ensure a clean seal.
6. Install New Parts: Install the new diaphragm, gaskets, and other components from the kit, ensuring they are correctly aligned.
7. Reassemble and Reinstall: Secure the pump housing, taking care not to overtighten the screws. Reinstall the pump onto the engine, attach fuel lines, and tighten all fittings.
8. Final Checks: Reconnect the battery. Prime the fuel system and carefully check for any leaks around the pump and fittings before starting the engine.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my engine?

A: First, check the compatibility tables on this page to ensure your engine's brand, model, HP, and year range are listed. For Mercury/Mariner models, it is crucial to also check your engine's serial number against the ranges provided in the "Notes" column. This kit is specifically for engines with square or triangular fuel pumps.

Q: What causes a fuel pump diaphragm to fail?

A: Diaphragms wear out over time due to constant flexing and exposure to fuel, especially ethanol blends, which can cause the material to stiffen or crack. Debris in the fuel system can also cause premature failure.

Q: What are the common signs of a failing fuel pump diaphragm?

A: Symptoms include the engine running rough, hesitating during acceleration, stalling at idle, or difficulty starting. You may also notice fuel weeping or leaking from the pump's exterior.

Q: OEM vs. Aftermarket?

A: 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.

Q: How fast do you ship and how much does it cost?

A: 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.

Q: What is your warranty and return policy?

A: 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.