Water Pump Impeller Kit - Fits Mercury/Mariner 30-70 HP Outboards (Replaces 77177A3, 46-77177A3)

Water Pump Impeller Kit – Fits Mercury/Mariner 30-70 HP Outboards

This water pump impeller rebuild kit is designed for Mercury and Mariner 30 HP to 70 HP 2-stroke outboard engines manufactured between 1977 and 1997. It provides all the necessary components to restore your engine's cooling system performance.

This kit is a direct replacement for multiple OEM and aftermarket part numbers, ensuring a precise fit and reliable function.

• Installation: Direct replacement for a straightforward installation.
• Complete Kit: Includes a new impeller, housing, plate, gaskets, and key for a full rebuild.
• Material: Features a durable rubber impeller and a corrosion-resistant metal housing.

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
• 1 x Drive Key
• 1 x Impeller Plate
• 1 x Gaskets Set
• 1 x Water Pump Housing

Installation Guide

1. Safety First: Disconnect the engine's battery and remove the spark plug wires to prevent accidental starting.
2. Drain Gear Lube: Place a drain pan under the lower unit and remove the upper and lower gear lube drain screws to drain the oil.
3. Remove Lower Unit: Remove the bolts securing the lower unit (gearcase) to the midsection. The number and location of bolts can vary, so check your service manual.
4. Access the Water Pump: With the lower unit removed, locate the water pump housing on top of the gearcase. Unbolt and remove the old housing.
5. Remove Old Components: Remove the old impeller, wear plate, and gaskets. Clean all mating surfaces thoroughly.
6. Install New Components: Place the new gasket and wear plate onto the gearcase. Slide the new drive key into the driveshaft keyway.
7. Install New Impeller: Lubricate the new impeller and housing interior with a small amount of dish soap or marine grease. Slide the new impeller onto the driveshaft while turning the shaft clockwise to bend the fins correctly.
8. Install New Housing: Place the new gasket on the housing and install the housing over the impeller, ensuring it seats correctly. Secure it with the bolts.
9. Reinstall Lower Unit: Guide the driveshaft back into the engine and reinstall the lower unit. Tighten the bolts to the manufacturer's specified torque.
10. Refill Gear Lube: Using a pump, fill the lower unit with fresh marine gear lubricant through the bottom drain hole until it seeps out of the upper hole. Reinstall both drain screws with new gaskets.
11. Final Check: Reconnect the battery and spark plug wires. Start the engine using a water supply (flushing muffs) and check for a strong, steady stream from the tell-tale outlet.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury or Mariner engine?

A: This kit is designed for 30-70 HP 2-stroke models made between 1977 and 1997. Please verify your engine's HP and year by checking its serial number plate. You can cross-reference the part numbers (46-77177A3, Sierra 18-3324) with your service manual or use the compatibility table on this page.

Q: My outboard is overheating, or the water stream from the "tell-tale" is weak. Could this kit fix it?

A: Yes, a weak or nonexistent water stream is a classic sign of a worn-out or failed water pump impeller. Replacing the impeller and housing with this kit is the most common solution to restore proper engine cooling.

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

A: For preventative maintenance, it is recommended to inspect the impeller annually and replace it every 1-2 years or 100-200 hours of use. This interval may be shorter if you operate in sandy, silty, or saltwater conditions.

Q: Is this an OEM part?

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.