Water Pump Impeller Repair Kit – Fits Mercury/Mariner 6-9.9 HP Outboards (Replaces 803748Q01, 803750A03, 853792A5)

Water Pump Impeller Repair Kit – Fits Mercury/Mariner 6-9.9 HP Outboards

This water pump impeller repair kit is designed for Mercury/Mariner 8 HP and 9.9 HP 4-Stroke (209cc) outboards from 2005 and newer with serial numbers R042475 and up. It provides a reliable solution for maintaining your engine’s cooling system.

This kit serves as a direct replacement for Mercury part numbers 803748Q01, 803750A03, 853792A5, 47-803748Q01, 47-803750A03, and 803748K01, as well as QuickMarine 803750A03.

• Includes a 6-blade neoprene impeller with a hardened nylon hub for durability.
• Comes with a complete set of gaskets, wear plate, and housing for a full service.
• Engineered for installation in the lower unit.

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 Water Pump Impeller (47-8037481)
• 1 x Water Pump Housing (803750A02)
• 1 x Insert Cup (8037511)
• 1 x Wear Plate (8037531)
• 1 x Gasket (161585)
• 1 x Gasket (161586)
• 1 x Gasket (161587)
• 1 x Installation Instructions

Installation Guide

1. Disconnect the Battery: Ensure the engine is off and disconnect the battery terminals to prevent accidental starting.
2. Drain Gearcase Oil: Place a drain pan under the lower unit and remove the upper and lower drain screws to drain the gearcase oil.
3. Remove the Lower Unit: Unbolt the lower unit (gearcase) from the upper leg of the outboard. This may also require disconnecting the shift shaft.
4. Access the Water Pump: With the lower unit removed, locate and unbolt the water pump housing.
5. Remove Old Components: Take note of the order of the components. Remove the old housing, impeller, wear plate, and gaskets. Clean the mounting surfaces thoroughly.
6. Install New Components: Install the new wear plate and gaskets. Slide the new impeller onto the driveshaft (turn the shaft clockwise to ease installation).
7. Install New Housing: Place the new housing over the impeller. Ensure the insert cup is correctly seated. Bolt the housing down to the specified torque.
8. Reassemble: Re-attach the lower unit to the outboard, ensuring the driveshaft, water tube, and shift shaft are correctly aligned.
9. Refill Gearcase Oil: Fill the gearcase with fresh marine gear lube through the bottom drain hole until it seeps out the top one. Reinstall both screws.
10. Test Operation: Reconnect the battery, start the engine in a test tank or with a water flusher, and verify that water is exiting the tell-tale "pee" hole.

Troubleshooting & FAQ

Q: How do I confirm this fits my Mercury 8 HP 4-stroke?

A: This kit fits specific Mercury 8 and 9.9 HP 4-stroke models (209cc) made in 2005 or later. The most important factor is your engine's serial number. It must be S/N R042475 or higher. Also ensure your model is a non-Bigfoot configuration. You can use the links provided in the "Compatible Engine Models" section to verify.

Q: What are the signs that my water pump impeller needs replacing?

A: The most common sign of a failing impeller is a weak or non-existent water stream from the "tell-tale" outlet. Other symptoms include the engine overheating alarm sounding or visible steam from the engine cowling. Over time, the neoprene blades can become brittle, stiff, or worn, reducing pumping efficiency.

Q: How often should I replace the water pump impeller?

A: As a general maintenance rule, it is recommended to inspect the impeller annually and replace it every 1-2 years or every 100-200 hours of operation, whichever comes first. This interval can be shorter if you frequently operate in sandy, silty, or saltwater environments.

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.