Water Pump Impeller Kit – Fits Mercury/Mariner 2-Cycle 30-70 HP (Replaces 46-77177A3, 77177A3)

Water Pump Impeller Kit – Fits Mercury/Mariner 2-Cycle 30-70 HP

This water pump impeller repair kit provides a complete solution for servicing the lower unit water pump on a wide range of Mercury and Mariner 2-stroke outboard engines from 30 HP to 70 HP (1976–1997). It is designed to restore cooling system performance and prevent engine overheating.

Directly replaces Mercury OEM part numbers 46-77177A3 and 77177A3, as well as aftermarket parts from Sierra, GLM, Mallory, and others, ensuring broad compatibility.

• Engine Compatibility: Fits various Mercury/Mariner 2-stroke 30-70 HP models, including 30 JET, 35, 40, 45, 50, 60, 65, and 70 HP.
• Complete Kit: Includes all necessary components for a full rebuild: impeller, housing, base, plates, gaskets, and hardware.
• Installation Type: Engineered as a direct OEM-equivalent replacement for a precise fit.

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 Impeller (47-20268)
• 1 x Impeller Plate (32768)
• 1 x Impeller Key
• 1 x Water Pump Housing (46-48746A1)
• 1 x Water Pump Base (46-77177A1)
• 1 x Water Pump Base Gasket (27-32771)
• 1 x Water Pump Base Gasket (27-77417)
• 1 x Lower Water Pump Gasket (27-32769)
• 1 x Upper Water Pump Gasket (27-19551)
• 2 x Drain Screw Gasket (12-19183)
• 1 x Rubber Washer (12-49221)
• 3 x O-Ring
• 1 x Exhaust Leg Rubber Seal (37721) - Note: This part is included in some kits but not all. Please verify if needed for your specific application.

Installation Guide

1. Safety First: Disconnect the battery and remove the spark plug wires. Secure the outboard in a suitable position.
2. Access the Lower Unit: Shift the outboard into neutral. Loosen and remove the bolts securing the lower unit (gearcase) to the upper leg.
3. Remove the Old Pump: Carefully drop the lower unit. The driveshaft will come with it. Unbolt and remove the old water pump housing to expose the impeller.
4. Inspect and Clean: Remove the old impeller, key, wear plate, and gaskets. Thoroughly clean all mating surfaces, removing any old gasket material or corrosion.
5. Install New Components: Place the new gaskets and wear plate onto the gearcase. Slide the new impeller key into the driveshaft keyway.
6. Install the Impeller: Lubricate the new impeller with a marine-safe grease or soapy water. Slide the impeller onto the driveshaft, turning the shaft clockwise to bed the vanes correctly.
7. Install the Housing: Apply lubricant inside the new housing. Press the housing down over the impeller, ensuring the vanes are correctly oriented, and align the bolt holes.
8. Secure and Reassemble: Secure the new housing with the provided bolts, tightening them to the manufacturer's specified torque.
9. Reinstall Lower Unit: Carefully guide the driveshaft back into the engine, ensuring the water tube and shift shaft align. Secure the lower unit with its bolts.
10. Final Checks: Reconnect the spark plug wires and battery. Test the engine using a water source (flushing muffs or in the water) and confirm a strong, steady stream from the cooling system's tell-tale outlet.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?
A: The most reliable method is to check your engine's model, horsepower, and serial number against our "Compatible Engine Models" table. For Mercury/Mariner models, the serial number is critical for identifying the correct year and model range, as there are often overlaps.

Q: What are the signs of a failing water pump impeller?
A: Common signs include an overheating engine alarm, a weak or non-existent water stream from the "tell-tale" outlet, or finding pieces of rubber in the cooling passages. A visual inspection may also reveal cracked, brittle, or missing impeller vanes.

Q: How often should the impeller be replaced?
A: As a general maintenance rule, it is recommended to inspect the impeller annually and replace it every 1-2 years or every 100-200 hours of use. Replacement frequency should be increased if operating in saltwater or sandy/silty 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.