Water Pump Repair Kit – Fits Mercury/Mariner 2-Cycle 30-70 HP Outboards (Replaces 77177A3)

Water Pump Repair Kit – Fits Mercury/Mariner 2-Cycle 30-70 HP Outboards (Replaces 77177A3)

This water pump repair kit is designed for Mercury/Mariner 2-Cycle 30-70 HP outboards manufactured between 1977 and 1997. It provides a complete solution for servicing and restoring your engine's cooling system to factory-fresh performance.

This kit is a direct replacement for Mercury/Mariner part numbers 77177A3 and 46-77177A3, as well as aftermarket parts Sierra 18-3324, GLM 12100, and Tutoroto 77177A3.

• Complete Kit: Includes a new impeller, upper and lower housings, gaskets, seals, and all necessary hardware for a full replacement.
• Fuel Type: Compatible with 2-Cycle gasoline outboard engines.
• Installation: Engineered as a direct replacement for the original OEM components without modifications.

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 Upper Housing
• 1 x Lower Housing
• 1 x Face Plate
• 1 x Face Seal
• 1 x Seal Carrier
• 1 x Water Tube Coupling
• 1 x Drive Key
• Multiple x Gaskets

Installation Guide

1. Safety First: Disconnect the battery and ensure the engine is turned off and cool to the touch.
2. Access the Lower Unit: Shift the outboard into neutral. Remove the bolts securing the lower unit (gearcase) to the upper engine housing.
3. Remove the Lower Unit: Carefully lower the gearcase away from the engine. You may need to disconnect the speedometer tube.
4. Disassemble the Water Pump: Locate the water pump assembly on top of the lower unit. Remove the bolts securing the water pump housing.
5. Inspect and Clean: Remove the old impeller, housing, gaskets, and wear plate. Clean all mating surfaces thoroughly, removing any old gasket material or debris.
6. Install New Components: Lightly lubricate the new housing interior. Install the new drive key and slide the new impeller onto the driveshaft, rotating it in the direction of engine operation.
7. Reassemble the Pump: Place the new gaskets, face plate, and seals correctly. Secure the new upper and lower housings with the provided bolts and tighten to the manufacturer's recommended torque.
8. Reinstall the Lower Unit: Realign the driveshaft, shift shaft, and water tube. Slide the lower unit back into place and secure it with the bolts. Reconnect the speedometer tube.
9. Test the System: Reconnect the battery. Start the engine in a suitable water source (using "earmuffs" or in the water) and check for a steady stream of water from the "tell-tale" outlet.

Troubleshooting & FAQ

How do I confirm this kit fits my specific engine?
The most reliable method is to check your engine's serial number against the ranges listed in the "Compatible Engine Models" table. Many Mercury/Mariner models have overlapping years, but different parts depending on the serial number. If unsure, use the serial number guide linked above.

What are the signs that my water pump needs to be replaced?
Common signs of a failing water pump include the engine overheating at low speeds, a weak or non-existent water stream from the tell-tale indicator, or a brittle or cracked impeller found during a visual inspection.

How often should I replace my water pump impeller?
As a general maintenance guideline, it is recommended to replace your outboard's water pump impeller every 1 to 2 years, or every 100-200 hours of operation, to prevent unexpected failures.

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.