Water Pump Repair Kit for Mercury/Mariner 30–70 HP Outboards – Replaces Mercury 46-77177A3

Product Details

This aftermarket Water Pump Repair Kit is designed for selected Mercury and Mariner outboard applications rated from 30 to 70 HP. It replaces Mercury OEM reference 46-77177A3 and is intended to renew the water pump components that support proper engine cooling.

The kit is associated with Mercury/Mariner cooling-system applications and should be matched to the engine's exact model, horsepower, and serial-number range before ordering. The same OEM reference can appear across different engine configurations, so horsepower alone is not sufficient for confirming fitment.

• Aftermarket replacement water pump repair kit.
• Includes the impeller, pump housing, base, plate, gaskets, drain hardware, and O-rings listed below.
• Suitable for servicing the water pump assembly when the listed application and serial-number conditions match.
• Replaces Mercury 46-77177A3; Sierra reference 18-3324 is also listed for this replacement application.

Part Number References

Engine & Model Compatibility

This kit is intended for selected Mercury and Mariner outboards in the 30–70 HP range. Confirm the complete model designation, horsepower, stroke configuration, and serial number against your service manual or the original pump components before purchase.

Important: The 30 JET and 40 HP applications above are tied to specific cataloged serial ranges. The broader 30–70 HP replacement range should not be treated as universal fitment for every engine in that horsepower range.

Technical Specifications

Product Type

Water pump repair kit

Application

Selected Mercury/Mariner outboard cooling-system applications

Rated Application Range

30–70 HP, subject to model and serial-number verification

Primary OEM Reference

Mercury 46-77177A3

Aftermarket Reference

Sierra 18-3324

Installation

Replacement installation in the water pump assembly

Product Status

Aftermarket replacement; not an OEM Mercury component

What's in the Box

Kit contents are based on the listed water pump kit configuration. Component reference numbers identify the corresponding service parts and are not separate products.

• 1 x Impeller, corresponding OEM reference 47-89983
• 1 x Upper water pump housing, corresponding OEM reference 46-77822A1
• 1 x Water pump base, corresponding OEM reference 46-73640A1
• 2 x Drain gasket, corresponding references 12-20260 and 12-19183
• 1 x Lower water pump base-to-face-plate gasket, corresponding references 27-32769 and 27-19553
• 1 x Upper face-plate-to-body gasket, corresponding references 27-32770 and 27-19551
• 1 x Water pump base gasket, corresponding reference 27-32771
• 1 x Water pump base gasket, corresponding references 27-77417 and 27-19552
• 1 x Drain plug, corresponding reference 12-49221-1
• 1 x Plate, corresponding reference 54705
• 1 x O-ring, corresponding reference 25-26855
• 1 x O-ring, corresponding reference 25-45711
• 1 x O-ring, corresponding reference 25-26722

Installation Notes

1. Disconnect the battery and place the outboard in neutral before beginning service.
2. Remove the lower unit according to the engine manufacturer's service procedure.
3. Remove the water pump housing and inspect the impeller, plate, housing, base, keyway, and driveshaft for wear or damage.
4. Clean all mating surfaces and remove old gasket material without damaging the sealing faces.
5. Install the replacement gaskets, plate, impeller, and other kit components in the same locations as the original parts.
6. Confirm that the impeller key is correctly seated and that the impeller vanes are oriented in the direction of driveshaft rotation.
7. Reinstall the pump housing and tighten fasteners to the torque specified in the engine service manual.
8. Reinstall the lower unit, ensuring correct alignment of the driveshaft, shift linkage, and water tube.
9. Run the engine only with an appropriate water supply and confirm a strong tell-tale stream before returning the boat to service.

Troubleshooting & FAQ

Safety & Important Information

• Verify the engine model, horsepower, stroke configuration, and serial number before ordering.
• Inspect the complete water pump assembly and replace any additional worn components required by the service manual.
• Use the manufacturer's torque specifications and installation procedures.
• Never run the outboard without an adequate water supply.
• Professional installation is recommended if you are not familiar with lower-unit or water-pump service.
• This is an aftermarket replacement, not an OEM Mercury component.

About Sea Sierra

• Marine Replacement Parts — Parts are selected for common marine repair and maintenance applications.
• Application-Focused Support — Match the complete engine and serial-number information before ordering.
• Aftermarket Value — Replacement components provide an alternative to purchasing the original manufacturer part.