Water Pump Impeller – Fits Mercury/Mariner 8-20 HP Four-Stroke Outboards (Replaces 47-803748)

Water Pump Impeller – Fits Mercury/Mariner 8-20 HP Four-Stroke Outboards (Replaces 47-803748)

This rubber impeller is a direct replacement for Mercury and Mariner 8, 9.9, 10, 15, and 20 HP four-stroke outboard motors manufactured between 2005 and 2023. As a crucial component of the cooling system, it ensures your engine maintains a safe operating temperature by circulating water efficiently.

This part is designed to meet or exceed original equipment specifications, providing a reliable and cost-effective solution for routine maintenance or repair.

• Installation Type: Direct replacement
• Housing Material: Durable neoprene rubber compound
• Compatible Models: Fits specific 2005-2023 Mercury/Mariner 8-20 HP 4-Stroke outboards

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 (Replaces 47-803748/47-8M0214944)

Installation Guide

Follow these steps for a successful installation. Professional installation is always recommended.

1. Disconnect the negative battery cable and remove the engine cover. Disconnect the shift linkage.
2. Loosen and remove the mounting bolts that attach the lower unit (gearcase) to the outboard's driveshaft housing. Carefully separate the lower unit.
3. Locate the water pump housing on top of the gearcase. Remove the bolts securing the housing cover.
4. Slide the water pump housing up the driveshaft to expose the old impeller. Note the rotational direction of the existing blades.
5. Remove the old impeller. Clean any debris or corrosion from the housing interior, wear plate, and cover.
6. Apply a light coat of marine-grade silicone grease to the inside of the pump housing and to the new impeller blades.
7. Slide the new impeller onto the driveshaft. Turn the driveshaft clockwise while pushing down to correctly "fold" the blades into the housing.
8. Reinstall the water pump housing and tighten the bolts to the manufacturer's specified torque.
9. Reattach the lower unit to the outboard, ensuring the driveshaft, water tube, and shift shaft are correctly aligned. Tighten bolts securely.

Troubleshooting & FAQ

Q: How do I confirm this impeller fits my specific engine?
A: The most reliable method is to match your engine's model and serial number against our compatibility table. Mercury serial numbers are critical for ensuring fitment, so use our linked guide to find yours.

Q: What are the signs of a failing water pump impeller?
A: Common symptoms include the engine overheating at idle or low speeds, and a weak or nonexistent water stream from the outboard's "tell-tale" indicator port.

Q: How often should I replace my outboard's impeller?
A: For preventative maintenance, it is recommended to replace the impeller every 1-2 years or every 100-200 hours of operation, depending on usage conditions (e.g., saltwater vs. freshwater).

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.