Water Pump Repair Kit – Fits Mercury/Mariner 30–70HP (Replaces 77177A3, 46-77177A3)
Water Pump Repair Kit – Fits Mercury/Mariner 30–70HP (Replaces 77177A3, 46-77177A3) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Water Pump Repair Kit – Fits Mercury/Mariner 30–70HP (Replaces 7717...
Water Pump Repair Kit – Fits Mercury/Mariner 30–70HP (Replaces 77177A3, 46-77177A3) is backordered and will ship as soon as it is back in stock.
Product Details
This complete Water Pump Repair Kit – Fits Mercury/Mariner 2-Stroke 30–70HP Outboards (Replaces 77177A3, 46-77177A3) is engineered to restore the cooling system on Mercury and Mariner 2-stroke outboard motors ranging from 30 to 70 HP, specifically for models manufactured between 1977 and 1997. The kit provides everything needed for a full water pump rebuild.
It serves as a direct interchange for Mercury/Mariner part numbers 77177A3 and 46-77177A3, as well as aftermarket references Sierra 18-3324, GLM 12100, and Mallory 9-48312.
- Designed for direct replacement of the original factory assembly.
- Includes all essential components: impeller, housings, gaskets, and seals.
- Compatible with standard 2-stroke outboard cooling systems.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/Mariner | 77177A3 |
| Mercury/Mariner | 46-77177A3 |
| Sierra | 18-3324 |
| GLM | 12100 |
| Mallory | 9-48312 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is designed for select Mercury and Mariner outboards. Please check your engine's serial number (SN) against the ranges provided to ensure an exact match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | Outboard | 30 HP Jet | 2-Stroke | 1977–1997 | 77177A3 | SN. C159200-G589999 |
| Mercury/Mariner | Outboard | 35 HP | 2-Stroke | 1977–1997 | 77177A3 | SN. 6445653-Up |
| Mercury/Mariner | Outboard | 40 HP | 2-Stroke | 1977–1997 | 77177A3 | SN. 4890103-6445653 |
| Mercury/Mariner | Outboard | 40 HP (4cyl) | 2-Stroke | 1977–1997 | 77177A3 | SN. C159200-Up |
| Mercury/Mariner | Outboard | 45 HP | 2-Stroke | 1977–1997 | 77177A3 | SN. 5531630-Up |
| Mercury/Mariner | Outboard | 50 HP (4cyl) | 2-Stroke | 1977–1997 | 77177A3 | SN. 4962056-Up |
| Mercury/Mariner | Outboard | 50 HP (3cyl) | 2-Stroke | 1977–1997 | 77177A3 | SN. 6428681-D000749 |
| Mercury/Mariner | Outboard | 60 HP | 2-Stroke | 1977–1997 | 77177A3 | SN. 6428681-D000749 |
| Mercury/Mariner | Outboard | 65 HP (3cyl) | 2-Stroke | 1977–1997 | 77177A3 | SN. 4382057-4571651 |
| Mercury/Mariner | Outboard | 70 HP | 2-Stroke | 1977–1997 | 77177A3 | SN. 4977157-B110053 |
Technical Specs
- Product Type
- Complete Water Pump Repair Kit
- Installation
- Direct replacement for original equipment
- Other Technical Attributes
- Compatible with 2-stroke outboard cooling systems
What’s in the Box
- 1 x Upper Pump Housing (18-3118)
- 1 x Lower Pump Housing/Water Pump Base (18-3424)
- 1 x Impeller (18-3007)
- 1 x Face Plate (18-3107)
- 1 x Drain Gasket (18-2945)
- 1 x Lower Water Pump Base to Face Plate Gasket (18-2823)
- 1 x Upper Face Plate to Body Gasket (18-2824)
- 1 x Water Pump Base Gasket (18-2825)
- 1 x Water Pump Base Gasket (18-2841)
- 1 x Drain Plug (18-2948)
- 1 x O-Ring (18-7155)
- 1 x O-Ring (18-7174)
- 1 x O-Ring (18-7115)
Installation Notes
- Disconnect the battery and shift linkage.
- Unbolt and carefully remove the lower unit (gearcase) from the outboard leg.
- Remove the old water pump housing bolts and lift the housing assembly off the driveshaft.
- Slide the old impeller off the driveshaft, taking note of the drive key's position. Remove old gaskets and the wear plate.
- Thoroughly clean all mating surfaces, ensuring they are free of old gasket material and corrosion.
- Install the new gaskets, wear plate, and drive key onto the driveshaft.
- Slide the new impeller onto the driveshaft. Rotate the driveshaft clockwise while pushing down to correctly seat the impeller vanes inside the new housing.
- Install the new housing and tighten bolts to the manufacturer's specified torque in a crisscross pattern.
- Apply a light coat of marine grease to the driveshaft splines and reinstall the lower unit, making sure the water tube, driveshaft, and shift shaft align correctly.
- Reconnect the shift linkage and battery. Start the engine using a water supply (flushing attachment or in water) and confirm a steady stream from the cooling system's tell-tale outlet.
Troubleshooting & FAQ
How do I know if my water pump is failing?
Common signs include a weak or non-existent stream of water from the "tell-tale" outlet, engine overheating alerts, or a melted/deformed pump housing upon inspection. Reduced engine performance at high RPMs can also indicate poor cooling.
What is the recommended replacement interval for an impeller?
For optimal reliability, most manufacturers recommend inspecting the impeller annually and replacing it every 1-2 years or every 100-200 hours of operation, depending on usage conditions (e.g., saltwater vs. freshwater).
My engine model is listed, but the serial number is different. Will this kit fit?
The serial number (SN) ranges are critical for ensuring correct fitment, as manufacturers often make mid-year design changes. We strongly recommend purchasing only if your engine's serial number falls within the specified ranges. If in doubt, contact us with your full engine details before ordering.
Is this a complete kit, or do I need to buy other parts?
This is a complete repair kit containing all the necessary components for a standard water pump rebuild, including the impeller, housings, gaskets, and O-rings as listed in the "What’s in the Box" section. No other parts should be required for a standard replacement.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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