Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9.9 HP (Replaces 803750A03, 3B2-87322-2)

Water Pump Impeller Repair Kit – Fits Mercury & Tohatsu 8/9.8/9.9 HP

This water pump impeller repair kit is designed for a range of Mercury, Tohatsu, and Nissan 4-stroke outboard motors, including Mercury 8-9.9 HP (209cc) models and Tohatsu/Nissan 8-9.8 HP MFS/NSF series engines. It provides a reliable solution for maintaining your engine's cooling system.

This kit serves as a direct replacement for Mercury part numbers 46-803750A03, 803750A03, 80375A03, 803748Q01, 803748K01 and Tohatsu part numbers 3B2873222M, 3B2873221M, 3B2873220M, 3B2-87322-2, 3B2-87322-1, 3B2-87322-0.

• Includes a marine-grade neoprene impeller, stainless steel housing components, gaskets, and hardware for a complete installation.
• Engineered to meet or exceed OEM specifications for fit, form, and function.
• Installation is a direct replacement for the original pump assembly.

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 Outboard Models

Tohatsu Outboard Models

Nissan Outboard Models

Technical Specifications

Package Contents

• 1 x Water Pump Impeller (8037481)
• 1 x Driveshaft Pin (9521811)
• 1 x Insert Cup (8037511)
• 1 x Wear Plate (8037531)
• 1 x Gasket (8M0072139)
• 1 x Gasket (8M0072138)
• 1 x Gasket (8M0072137)
• 4 x Bolts and Washers (879194305)

Installation Guide

1. Safety First: Disconnect the battery and remove the spark plug wires to prevent accidental starting.
2. Access the Lower Unit: Shift the outboard into neutral. Remove the bolts securing the lower unit (gearcase) to the upper leg.
3. Remove the Lower Unit: Carefully lower the gearcase away from the engine. The driveshaft will disengage from the powerhead.
4. Open the Water Pump Housing: Locate the water pump assembly on top of the gearcase. Remove the bolts securing the housing cover.
5. Replace Components: Take note of the old parts' orientation. Remove the old impeller, wear plate, gaskets, and insert cup. Clean all mating surfaces thoroughly.
6. Install New Parts: Install the new wear plate, gaskets, and insert cup. Slide the new impeller onto the driveshaft, rotating it clockwise to bend the vanes correctly as you lower the housing over it.
7. Reassemble Housing: Apply a light coat of marine grease to the inside of the housing. Secure the housing cover with its bolts, tightening them to the manufacturer's specified torque.
8. Reinstall Lower Unit: Guide the driveshaft back into the powerhead, ensuring the water tube and shift shaft align. Secure the lower unit with its bolts.
9. Test Operation: Reconnect the battery and spark plug wires. Start the engine in a test tank or with a water flusher to ensure a strong, steady stream of water from the tell-tale outlet.

Troubleshooting & FAQ

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

A: The best way is to match your engine's model and serial number against the compatibility tables above. You can also use the "Part Number Cross-Reference" table to verify if this kit replaces your existing part number. For Mercury owners, our serial number guide can help you locate this information.

Q: What are the common signs of a failing water pump impeller?

A: The most common signs include the engine running hotter than normal, an engine overheating alarm, and a weak or non-existent water stream from the "tell-tale" outlet. Visible damage to the old impeller, such as cracked, brittle, or missing vanes, also indicates it's time for a replacement.

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

A: For preventative maintenance, it is recommended to inspect and/or replace the impeller every 1 to 2 years or every 100 to 200 hours of operation, whichever comes first. This interval can vary based on usage 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.