Water Pump Kit with Housing – Fits Mercury/Mariner/Tohatsu 9.9-20 HP EFI (Replaces 8M0137849, 8M0135821)

Water Pump Kit with Housing – Fits Mercury/Mariner/Tohatsu 9.9-20 HP EFI

This complete water pump repair kit is designed for Mercury/Mariner 9.9-20 HP 4-Stroke EFI outboards (2013 and newer) and Tohatsu/Nissan MFS15E & MFS20E 4-Stroke models. It provides all necessary components to restore your engine's cooling system performance.

This kit is a direct replacement for Mercury part numbers 8M0137849, 98-8M0135821, 8M0134484, and 46-8M0122064, as well as Tohatsu/Nissan part numbers 3RS-87322-1 and 3RS-87322.

• Includes the impeller, housing, wear plate, insert cup, gaskets, key, and seals for a comprehensive service.
• Mounts on the lower unit of the outboard motor.
• Features a durable Marine Grade CR-Neoprene impeller and a Marine Grade SS316 (Stainless Steel) wear plate for longevity.

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 Impeller (334-65021 / 3LD-65021)
• 1 x Housing
• 1 x Insert Cup
• 1 x Wear Plate
• 2 x Gaskets
• 1 x Key
• 1 x Seal Kit
• 1 x Installation Instructions

Installation Guide

1. Disconnect the battery and shift the outboard into neutral.
2. Remove the lower unit bolts to carefully separate it from the upper casing.
3. Locate and unbolt the water pump housing.
4. Remove the old housing, impeller, wear plate, and gaskets. Clean all mating surfaces thoroughly.
5. Install the new key, gaskets, wear plate, and impeller into the new housing. Ensure the impeller vanes are oriented correctly.
6. Slide the new water pump assembly down the driveshaft and secure it with its bolts.
7. Reinstall the lower unit, making sure the driveshaft, shift shaft, and water tube align correctly.
8. Tighten all bolts to the manufacturer's specified torque and reconnect the battery.
9. Test the engine on a water source (flusher or test tank) to confirm proper water circulation from the tell-tale outlet.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?
A: This kit is designed for specific serial number ranges. For Mercury/Mariner 9.9-20 HP EFI models, it fits serials 1R00814+ and 0R833820+ (2013 and newer). It also fits Tohatsu/Nissan MFS15E and MFS20E models from 2013 and newer. Always verify your engine's serial number before ordering.

Q: What are the signs my water pump is failing?
A: Common symptoms include a weak or non-existent water stream from the "telltale" outlet, engine overheating alerts or alarms, and steam from the exhaust. Upon inspection, a worn, brittle, or melted impeller confirms failure.

Q: How often should I replace the water pump impeller?
A: For optimal performance and engine safety, we recommend inspecting the impeller annually and replacing it every 1-2 years or 100-200 hours of use. More frequent replacement may be necessary if you operate in sandy, silty, or saltwater conditions.

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.