Water Pump Impeller Kit with Housing – Fits Mercury/Mariner 2-Stroke 30-70 HP (Replaces 46-77177A3, Sierra 18-3324)

Water Pump Impeller Kit with Housing – Fits Mercury/Mariner 2-Stroke 30-70 HP (Replaces 46-77177A3, Sierra 18-3324)

This water pump impeller repair kit provides a complete solution for servicing the cooling system on specific Mercury and Mariner 2-stroke outboard engines, ranging from 30 HP to 70 HP (1977–1997). It is designed as a direct replacement for OEM and other aftermarket part numbers to restore cooling performance and prevent engine overheating.

This kit directly replaces Mercury part number 46-77177A3, Quicksilver 77177A3, Sierra 18-3324, GLM 12100, and Mallory 9-48312.

• Includes a new neoprene impeller, stainless steel plate, gaskets, and complete upper/lower plastic housing for a full rebuild.
• Engineered as a direct-fit replacement for straightforward installation.
• Restores lost cooling performance caused by a worn, brittle, or damaged impeller.

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 Complete Water Pump Kit (46-77177A3) including:
  • 1 x Water Pump Impeller
  • 1 x Impeller Plate
  • 1 x Impeller Key
  • 1 x Water Pump Housing
  • 1 x Water Pump Base
  • 1 x Water Pump Base Gasket
  • 1 x Lower Gasket
  • 1 x Upper Gasket
  • 1 x Drain Screw Gasket
  • 1 x Rubber Washer
  • 1 x O-Ring
  • 1 x Water Tube Coupling

Installation Guide

Always consult your engine’s service manual before beginning work. The general process is as follows:

1. Disconnect the battery and shift the outboard into neutral.
2. Place a drain pan under the lower unit and remove the gearcase lubricant drain screw to empty the oil.
3. Remove the bolts securing the lower unit (gearcase) to the midsection.
4. Carefully lower the gearcase away from the engine. The driveshaft will slide out.
5. Unbolt and remove the old water pump housing assembly from the gearcase.
6. Remove the old impeller, woodruff key, wear plate, and any gaskets. Note their orientation.
7. Thoroughly clean the driveshaft and all mating surfaces to remove old gasket material and corrosion.
8. Install the new lower gasket, wear plate, and woodruff key.
9. Slide the new impeller onto the driveshaft over the key, turning the shaft clockwise to seat the vanes correctly.
10. Install the new housing and gaskets, then tighten the bolts to the specified torque.
11. Re-install the lower unit, ensuring the driveshaft, shift shaft, and water tube align correctly.
12. Refill the gearcase with fresh lubricant, install a new drain screw gasket, and connect a water supply before starting the engine to test.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?

A: The most reliable method is to cross-reference your engine's model, year, and serial number with the detailed "Compatible Engine Models" table on this page. For many Mercury/Mariner models, the serial number range is critical for confirming the correct part. This kit is a direct replacement for OEM part number 46-77177A3.

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

A: Common signs of a bad impeller include the engine overheating at idle or low speeds, a weak or intermittent water stream from the "telltale" outlet, or in severe cases, a complete lack of water discharge. The impeller is a rubber component that can become brittle, cracked, or worn over time, reducing its ability to pump water effectively.

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

A: As a preventative maintenance best practice, the impeller should be inspected annually and replaced every 1-2 years or every 100-200 hours of operation. Replacement frequency should be increased for engines operated in saltwater, silty, or sandy conditions.

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.