Water Pump Impeller – Fits Mercury/Mariner 4–9.8HP Outboards (Replaces 47-89981, 47-65957, 47-39074)

Water Pump Impeller – Fits Mercury/Mariner 4–9.8HP Outboards (Replaces 47-89981, 47-65957, 47-39074)

This water pump impeller is designed for specific Mercury/Mariner 4, 4.5, 6, 7.5, and 9.8 HP 2-stroke outboard engines (1975–1986) that are equipped with a 0.456" (11.6mm) diameter drive shaft. Please verify your shaft diameter before ordering, as some engine models used multiple shaft sizes.

It serves as a direct replacement for Mercury part numbers 47-89981, 47-89981B, 47-65957, and 47-39074, and is also interchangeable with several aftermarket parts, including Sierra 18-3039 and GLM 89810.

• Installation Method: Direct replacement with a press-fit connection on the drive shaft.
• Durable Construction: Made from high-quality neoprene rubber with a solid brass hub for reliable performance and corrosion resistance.
• Critical Component: Essential for maintaining proper engine cooling and preventing overheating.

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 47-89981)

Installation Guide

1. Prepare the Engine: Disconnect the spark plug wires and the battery. Turn off the fuel supply.
2. Access the Lower Unit: Place the outboard motor in a secure position and remove the lower unit (gearcase) by undoing the mounting bolts.
3. Remove the Water Pump Housing: Locate the water pump assembly on top of the lower unit. Unscrew the bolts securing its housing and lift the housing off.
4. Inspect and Remove Old Impeller: Note the rotational direction of the old impeller's blades before pulling it off the drive shaft. You may need a small pry tool.
5. Clean Components: Remove the old gaskets and wear plate. Thoroughly clean the housing interior, wear plate surface, and drive shaft.
6. Install New Impeller: Slide the new impeller onto the drive shaft. Turn the shaft in its normal direction of rotation while pushing down to help seat the blades correctly within the housing.
7. Reassemble the Pump: Place the new gaskets and wear plate, then reinstall the pump housing. Tighten the bolts to the manufacturer's recommended torque specifications.
8. Reinstall Lower Unit: Carefully guide the lower unit back into place, ensuring the drive shaft, shift shaft, and water tube align correctly. Secure it with the mounting bolts.
9. Final Checks: Reconnect the spark plug wires and battery. Test the engine in a water tank or on the water, and confirm a strong, steady stream of water is exiting the tell-tale outlet.

Troubleshooting & FAQ

Q: How do I confirm this impeller fits my Mercury/Mariner engine?

A: This impeller is specifically for Mercury/Mariner 4–9.8 HP 2-stroke outboards (1975–1986) that use a 0.456" (11.6mm) diameter drive shaft. It is critical to measure your shaft diameter before ordering, as some models in the same serial number range used a different, smaller shaft. This part will not fit 5HP models, which require a different part number.

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

A: For optimal performance and engine safety, we recommend inspecting your impeller annually and replacing it every 1-2 years or every 100-200 hours of operation, whichever comes first. Usage in saltwater or sandy/silty conditions may require more frequent replacement.

Q: What are the signs of a failing impeller?

A: The most common signs of a worn or failed impeller are a weak or non-existent water stream from the "tell-tale" outlet, and the engine temperature alarm activating or the engine visibly overheating. The blades can become brittle, cracked, or lose their flexible shape over time.

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, especially the drive shaft diameter (0.456"), 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. All mentions of brand names and part numbers are for reference purposes only.
• Professional installation is recommended to ensure safety and optimal performance. Improper installation can lead to engine damage.

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.