Water Pocket Cover Kit – Fits Mercury/MerCruiser R/MR/Alpha One (Replaces 42724A3)
Water Pocket Cover Kit – Fits Mercury/MerCruiser R/MR/Alpha One (Replaces 42724A3) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Water Pocket Cover Kit – Fits Mercury/MerCruiser R/MR/Alpha One (Re...
Product Details
This Water Pocket Cover Kit is a direct-fit replacement for various Mercury/MerCruiser R, MR, and Alpha One sterndrive models manufactured from 1963 to 1991. The cover bolts to the bottom of the upper unit and is essential for proper water circulation from the water pump.
It provides a direct interchange for Mercury/MerCruiser part numbers 42724A3, 32489A2, and 54235A2, as well as aftermarket equivalents including Sierra 18-3219, GLM 12200, and Mallory 9-78139.
- Installs on the bottom of the upper sterndrive unit.
- Receives and directs water flow from the water pump.
- Kit includes the cover and necessary mounting hardware.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury/MerCruiser | 42724A3 |
| Mercury/MerCruiser | 32489A2 |
| Mercury/MerCruiser | 54235A2 |
| Sierra | 18-3219 |
| GLM | 12200 |
| Mallory | 9-78139 |
Engine & Model Compatibility
Confirm your engine model and year range in the table below to ensure correct fitment.
This component is designed exclusively for the following Mercury/MerCruiser Stern Drive models.
| Brand | Model | Rated HP | Years | OEM Part No. |
|---|---|---|---|---|
| MerCruiser | I | Various | 1963 | 42724A3 |
| MerCruiser | IA/IB/IC | Various | 1964 | 42724A3 |
| MerCruiser | IA/IB/IC EZ-SHIFT | Various | 1965–1966 | 42724A3 |
| MerCruiser | 120/140 | 120/140 | 1967–1982 | 42724A3 |
| MerCruiser | 160 | 160 | 1967–1969 | 42724A3 |
| MerCruiser | 165 | 165 | 1970–1981 | 42724A3 |
| MerCruiser | 225-S | 225 | 1974 | 42724A3 |
| MerCruiser | 233 | 233 | 1975–1977 | 42724A3 |
| MerCruiser | 470 | 170 | 1976–1982 | 42724A3 |
| MerCruiser | 485 | 185 | 1980–1982 | 42724A3 |
| MerCruiser | 888 | 188 | 1971–1982 | 42724A3 |
| MerCruiser | 898/228 | 228 | 1977–1982 | 42724A3 |
| MerCruiser | 250 | 250 | 1977 | 42724A3 |
| MerCruiser | 260 | 260 | 1978–1982 | 42724A3 |
| MerCruiser | R/MR/ALPHA ONE (STERNDRIVE) | Various | 1983–1991 | 42724A3 |
| MerCruiser | R/MR/ALPHA ONE (TRANSOM ASSEMBLY) | Various | 1983–1991 | 42724A3 |
Technical Specs
- Product Type
- Water Pocket Cover Kit
- Installation
- Bolts to bottom of upper unit
- Connection
- Receives water from water pump
- Dimensions
- 6.0" L x 11.0" W x 1.69" H
- Warranty
- 1 Year (Candy Marine)
- Other Technical Attributes
- Fits on the bottom of the upper unit and receives the water from the water pump
What’s in the Box
- 1 x Water Pocket Cover Kit (42724A3/32489A2/54235A2)
Installation Notes
- Safely secure the vessel and disconnect the battery.
- Position a drain pan and drain the gear lube from the sterndrive.
- Carefully unbolt and remove the old, damaged water pocket cover and gasket.
- Thoroughly clean the mounting surface on the upper unit, ensuring it is free of old gasket material and corrosion.
- Place the new gasket onto the unit, followed by the new water pocket cover.
- Install the mounting bolts and tighten them to the manufacturer's specified torque in a crisscross pattern.
- Refill the sterndrive with the correct type and amount of gear lube.
- Reconnect the battery. After launching, check for any signs of water leaks around the new cover.
Troubleshooting & FAQ
How do I know if this cover fits my sterndrive?
This kit is designed for MerCruiser R, MR, and Alpha One drives from 1963 to 1991. The most reliable way to confirm fitment is to match your original part number to the ones listed in our Part Number Matrix (42724A3, 32489A2, etc.) or find your specific engine model in the compatibility table.
What are the signs of a failing water pocket cover?
Common signs include visible cracks or corrosion, water leaks from the cover area, or engine overheating issues if the cover fails completely and disrupts cooling water flow. Regular inspection during maintenance is recommended.
Is a gasket included with this kit?
Yes, this is a complete kit that typically includes the cover and the necessary gasket for installation. You should not need to purchase a separate gasket.
What is the function of the water pocket cover?
The water pocket cover is a critical component of the sterndrive's cooling system. It creates a sealed passage that channels cooling water from the water pump up into the engine, preventing leaks and ensuring efficient heat exchange.
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.
Payment & Security
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