Water Pump Repair Kit – Fits Mercury/Mariner Outboards & MerCruiser Alpha One

Water Pump Repair Kit – Fits Mercury/Mariner Outboards & MerCruiser Alpha One

This water pump repair kit is designed for a wide range of Mercury/Mariner outboards from 65 to 225 HP (4-cylinder through V-6 models with short-vane impellers) and MerCruiser Alpha One, I, R, and MR stern drives with serial numbers 2491586 to 0D469858 (1970–1990).

It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 46-96148Q8, 46-96148A8, 46-96148T8, 46-96148A5, 46-96148B8, Sierra 18-3217, and GLM 12280.

• Installation Type: Direct replacement for the upper water pump housing.
• Key Components: Includes plastic upper housing, impeller, face plate, gaskets, seals, and drive key.
• Important Note: This kit repairs the upper section of the water pump; it does not include the water pump base.

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.

Mercury/Mariner Outboards

MerCruiser Stern Drives

Technical Specifications

Package Contents

• 1 x Water Pump Impeller (47-89984T-3)
• 1 x Plastic Pump Housing Assembly
• 1 x Face Plate
• 1 x Gasket Set (multiple gaskets)
• 1 x Drive Key
• 1 x Face Seal
• 1 x Seal Carrier
• 1 x Water Tube Coupling
• 1 x O-ring Set (multiple O-rings)
• 2 x Gear Lube Fill & Vent Screw Seals
• Note: This kit includes components for upper housing repair only and does not include the water pump base.

Installation Guide

1. Safety First: Disconnect the battery and ensure the engine is off and cool.
2. Access the Lower Unit: Drain the gearcase oil and detach the lower unit from the outboard leg or stern drive.
3. Remove Old Pump: Unscrew the bolts securing the water pump housing. Carefully lift the housing off the driveshaft.
4. Inspect and Clean: Remove the old impeller, gaskets, and wear plate. Clean all mating surfaces thoroughly.
5. Install New Components: Place the new gasket and wear plate onto the base. Slide the new drive key and impeller onto the driveshaft.
6. Assemble New Housing: Lubricate the inside of the new housing and install it over the impeller, ensuring the blades are turned in the correct rotational direction.
7. Secure Housing: Apply new seals and O-rings as included in the kit. Bolt the new housing down to the correct torque specifications.
8. Reassemble: Reattach the lower unit to the engine, refilling the gearcase with fresh oil.
9. Test: Reconnect the battery and start the engine using a water supply (flushing muffs). Check for a steady stream of water from the tell-tale outlet.

Troubleshooting & FAQ

How do I confirm this kit fits my engine?
The most reliable method is to match your engine's serial number to the ranges listed in the compatibility tables. This kit fits specific MerCruiser Alpha One drives (and pre-Alpha models) from 1970-1990 and a broad range of Mercury/Mariner outboards. Check the HP, year, and serial number before ordering.

What are the signs of a failing water pump?
Common symptoms include the engine overheating at idle or low speeds, a weak or non-existent water stream from the "tell-tale" outlet, and in severe cases, a steam cloud from the exhaust. The impeller is a wear item and should be inspected regularly.

How often should the water pump impeller be replaced?
As a general maintenance guideline, the impeller should be inspected annually and replaced every 1-2 years, or every 100-200 hours of operation, depending on usage conditions. Operating in sandy or silty water may require more frequent replacement.

OEM vs. Aftermarket?
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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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.