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

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

This water pump impeller is a direct-fit replacement for a range of Mercury/Mariner 2-Stroke outboards from 3.9 HP to 10 HP (model years 1965–1986) that utilize an 11.60 mm shaft diameter. It is designed to restore cooling system performance and prevent engine overheating.

It directly replaces Mercury Part Number 47-89981 and serves as an aftermarket equivalent for Sierra 18-3039, GLM 12270, CEF 500314, and Mallory 9-45305.

• Installation Method: Direct-fit replacement for the original impeller.
• Included Components: This package contains the water pump impeller only. Gaskets and housing are not included.
• Engine Compatibility: Fits specific gasoline 2-stroke outboards. Warning: Not compatible with 5 HP Mercury Mariner engines.

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)
• Note: This is the impeller only. Gaskets, wear plates, and housing are sold separately.

Installation Guide

1. Disconnect the engine's battery and shut off the fuel supply.
2. Place the outboard in neutral and remove the lower unit (gearcase) bolts.
3. Carefully lower and remove the gearcase to access the water pump.
4. Remove the bolts securing the water pump housing cover.
5. Slide the old impeller off the driveshaft. Note the direction of the blade rotation for correct installation of the new one.
6. Inspect the wear plate and housing for grooves, scoring, or warping. Replace if significant wear is found.
7. Lightly lubricate the interior of the pump housing and the new impeller with marine grease.
8. Slide the new impeller onto the driveshaft while turning the shaft clockwise to correctly orient the blades.
9. Reinstall the water pump housing and tighten the bolts to the manufacturer's specified torque.
10. Reattach the lower unit, ensuring the driveshaft and water tube align correctly.
11. Once secured, reconnect the battery and test the engine using a flush-out device ("muffs") to confirm water flows from the tell-tale port.

Troubleshooting & FAQ

Q: How do I confirm this impeller fits my Mercury outboard?

A: This impeller fits specific Mercury/Mariner 2-stroke models from 3.9 HP to 10 HP (1965–1986) with an 11.60 mm internal shaft diameter. Please check the "Compatible Engine Models" table and verify your engine's serial number. Crucially, it is not compatible with 5 HP Mercury Mariner engines.

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

A: For optimal engine protection, we recommend replacing the impeller every 1-2 years or every 100-200 hours of use, depending on operating conditions (e.g., saltwater vs. freshwater, high-sand environments).

Q: What are the signs of a failing impeller?

A: Common signs include a weak or non-existent water stream from the tell-tale port, engine overheating alarms, a melted or deformed water pump housing, or a noticeable drop in water pressure readings if your vessel is equipped with a gauge.

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.