Water Pump Impeller Kit – Fits Mercury 9.9-20 HP 4-Stroke (Replaces 8M0135821, 8M0137849)

Water Pump Impeller Kit – Fits Mercury 9.9-20 HP 4-Stroke (Replaces 8M0135821, 8M0137849)

This water pump impeller repair kit is designed for Mercury Mariner 4-Stroke outboards, including 9.9, 10, 15, and 20 HP (333cc, 2-Cylinder) models from 2020 and newer with serial numbers 0R833820 and above. It covers ProKicker and SeaPro variants. The kit is also compatible with Tohatsu/Nissan MFS 15-20 HP outboards that utilize an equivalent cooling system design.

It serves as a direct replacement for multiple OEM part numbers, providing a reliable and complete solution for maintaining your engine's cooling system. Use the cross-reference table below to verify compatibility.

• Complete kit includes impeller, housing, face plate, gaskets, and seals for a full repair.
• Engineered for a direct fit, ensuring a straightforward installation process.
• Constructed with corrosion-resistant materials for enhanced durability in marine environments.

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.

Mercury/Mariner

Nissan/Tohatsu

Technical Specifications

Package Contents

• 1 x Water Pump Impeller
• 1 x Impeller Housing
• 1 x Face Plate
• 2 x Gasket
• 1 x Key
• 1 x Seal Kit
• 1 X Insert Cup

Note: Silicone grease, glycerin, or dish soap is recommended for installation but not included in this kit.

Installation Guide

1. Disconnect the negative battery cable and ensure the engine is off.
2. Unbolt and carefully separate the lower unit (gearcase) from the upper engine housing.
3. Locate and remove the bolts securing the water pump housing.
4. Slide the old housing and impeller off the driveshaft. Note the rotational direction of the old impeller fins.
5. Thoroughly clean the driveshaft and mating surfaces where the new components will sit.
6. Install the new gasket and face plate onto the gearcase.
7. Slide the new impeller onto the driveshaft, rotating it in the correct clockwise direction.
8. Lubricate the inside of the new pump housing with a marine-safe lubricant (not included) and install it over the impeller, pressing down while turning the driveshaft.
9. Secure the housing with its bolts, tightening them to the torque specified in your service manual.
10. Re-attach the lower unit to the engine, ensuring the driveshaft, water tube, and shift shaft align correctly. Test operation in water.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury engine?
A: This kit fits 2020 and newer Mercury/Mariner 9.9-20 HP 4-stroke models with serial numbers 0R833820 and above. Please verify your serial number and check the compatibility table before ordering.

Q: What are the signs of a failing water pump impeller?
A: Common signs include a weak or non-existent water stream from the "telltale" outlet, engine overheating alarms, and reduced engine performance. A damaged impeller can cause severe engine damage if not replaced.

Q: How often should the water pump impeller be replaced?
A: For preventative maintenance, it is recommended to inspect the impeller annually and replace it every 1-2 years or every 100-200 hours of use, depending on operating conditions (e.g., saltwater vs. freshwater, sandy/silty water).

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.