803529T04 3H8-04000-1 Fuel Pump Assembly for Mercury Tohatsu | JLM Marine

Fuel Pump Assembly – Fits Mercury Mariner & Tohatsu 4-Stroke Outboards

This fuel pump assembly is engineered for Mercury Mariner 4-stroke outboards ranging from 10 HP to 30 HP, as well as Tohatsu 4-stroke models including MFS 9.9B2, MFS 9.9C, MFS 15B2, MFS 15C, MFS 18B2, and MFS 18C. It delivers reliable fuel delivery for both carbureted and EFI systems across 2-cylinder and 3-cylinder configurations.

This part directly replaces OEM numbers 803529T04 (Quicksilver/Mercury), 3H8-04000-1 (Tohatsu), and 5041064, ensuring seamless compatibility with your original equipment.

• Complete assembly includes fuel pump, O-ring, and 2 mounting clips
• Suitable for both carbureted and electronic fuel injection (EFI) engines
• Designed for 2-cylinder and 3-cylinder 4-stroke outboard configurations

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

Your purchase includes the following components:

• 1 × Fuel Pump Assembly
• 1 × O-ring
• 2 × Mounting Clips

Installation Guide

1. Disconnect the battery and relieve fuel system pressure by squeezing the primer bulb until soft.
2. Locate the existing fuel pump on your outboard engine and take a photo for reference during reassembly.
3. Carefully disconnect the fuel lines from the old pump, noting their positions. Have a rag ready to catch any fuel spillage.
4. Remove the mounting clips or bolts securing the old fuel pump to the engine block.
5. Gently pull the old pump away from the engine, taking care not to damage the mating surface.
6. Clean the mounting surface on the engine block, removing any old gasket material or debris.
7. Install the new O-ring onto the fuel pump, ensuring it is seated properly in its groove.
8. Position the new fuel pump assembly onto the engine block, aligning it with the mounting holes.
9. Secure the pump using the two provided clips, ensuring they snap firmly into place or torque bolts to manufacturer specifications.
10. Reconnect the fuel lines to the corresponding inlet and outlet ports on the new pump, ensuring a tight fit.
11. Reconnect the battery and prime the fuel system by squeezing the primer bulb until firm.
12. Start the engine and inspect for fuel leaks around the pump connections; re-tighten if necessary.

Troubleshooting & FAQ

Q: How do I confirm this fuel pump fits my specific engine?
A: Cross-reference your engine model and serial number with the compatibility table above. For Mercury engines, verify the serial number range matches (e.g., 15 HP Carb requires serial 0R235949 & up). If uncertain, send us a photo of your engine's nameplate for confirmation.

Q: What are the signs that my fuel pump needs replacement?
A: Common symptoms include difficulty starting, engine stalling or hesitation under load, reduced top speed, inconsistent RPM, or visible fuel leaks around the pump. A hard primer bulb that won't stay firm also indicates pump failure.

Q: How often should I replace the fuel pump?
A: Fuel pumps don't have a fixed replacement interval but should be inspected annually. Replace immediately if you notice performance issues, leaks, or cracks in the pump housing. Typical lifespan ranges from 3–7 years depending on usage and fuel quality.

Q: Will this work on both carbureted and EFI engines?
A: Yes, this fuel pump is designed for both carburetor-equipped 2-cylinder models (10, 15, 20 HP) and EFI-equipped 3-cylinder models (25, 30 HP) as listed in the compatibility table.

Q: What's the difference between this aftermarket pump and the OEM version?
A: This is an aftermarket replacement part (not an OEM component). We manufacture to OEM specifications using comparable-grade materials in an ISO9002-certified facility. Each batch is inspected for consistent performance, offering reliable operation at a more competitive price point than OEM.

Q: Is this an OEM part or 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.