Complete Water Pump Kit – Fits MerCruiser Alpha One Gen 1 (Replaces 46-96148A8, 12120)

$49.99 $79.00

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Complete Water Pump Kit – Fits MerCruiser Alpha One Gen 1 (Replaces 46-96148A8, 12120) is backordered and will ship as soon as it is back in stock.

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This Complete Water Pump Kit is designed for MerCruiser Alpha One Generation 1 sterndrive units with serial numbers 6225577 and up, covering models from 1984 to 1990. It provides all necessary components to restore the engine's cooling system performance and prevent overheating.

It serves as a direct replacement for MerCruiser part numbers 46-96148A8, 96148A5, 96148B8, and 46-96148T8, and interchanges with Bombardier, GLM, and Sierra equivalents.

Engineered for direct installation on Alpha One Gen 1 sterndrives.
Restores cooling efficiency and prevents damage from impeller failure.
Includes the housing, impeller, gaskets, and all other required components.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
MerCruiser	46-96148A8 / 96148A5 / 96148B8 / 96148T8
Bombardier	0508395 / 0508399 / 0508400 / 0508402 / 0508403 / 0508404 / 0508406 / 0508414 / 0509047
GLM	12120
Sierra	18-3320

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For MerCruiser applications, verify your sterndrive's serial number is within the range of 6225577 to OD469858 to ensure correct fitment.

Brand	Model	Rated HP	Years	OEM Part No.	Notes
MerCruiser	Alpha One Gen 1	All	1984–1990	46-96148A8	Serial numbers 6225577 to OD469858
MerCruiser	MR	All	1984–1990	46-96148A8	Serial numbers 6225577 to OD469858

Technical Specs

Product Type: Complete Water Pump Kit
Installation: Direct replacement for Alpha One Gen 1 sterndrive
Dimensions: 15.0" L x 11.0" W x 11.0" H
Fitment: For sterndrive units with serial numbers 6225577 and up

What’s in the Box

1 x Complete Water Pump Kit (46-96148A8)
1 x Impeller (47-89984T4)
1 x Key (28-56654)
1 x Pump Housing (46-96148T1)
1 x Pump Base (46-44292A3)
1 x Guide Tube (23-29804T)
1 x Cup (48752)
1 x Wear Plate (32435)
1 x Gasket (27-85608-1)

Installation Notes

Disconnect the battery and ensure the engine is off and cool.
Place the sterndrive in the full "down" and "in" position. Drain the gear lube from the lower unit.
Remove the propeller and the lower unit mounting bolts.
Carefully separate the lower unit from the upper housing, watching for the shift shaft.
Unbolt and remove the old water pump housing and its components from the lower unit.
Clean the mounting surfaces thoroughly, removing any old gasket material or sealant.
Assemble the new water pump kit components in the reverse order of disassembly, ensuring the impeller key is correctly placed.
Lightly grease the new gaskets and O-rings before installation.
Guide the new pump assembly onto the driveshaft and secure it.
Reinstall the lower unit, ensuring the water tube, shift shaft, and driveshaft align correctly.
Refill the gear lube and reinstall the propeller.
Reconnect the battery and test the engine's cooling system at the dock before heading out on the water.

Troubleshooting & FAQ

How do I know if this kit fits my engine?

This kit is specifically for MerCruiser Alpha One Generation 1 sterndrives (1984–1990) with serial numbers from 6225577 to OD469858. Please verify your drive's model and serial number before ordering.

What are the signs of a failing water pump?

Common symptoms include the engine running hotter than normal, a weak or non-existent water stream from the tell-tale outlet, and steam from the exhaust. A damaged impeller can also cause a rattling noise.

How often should the water pump impeller be replaced?

For preventative maintenance, it is recommended to inspect the impeller annually and replace it every 1-2 years or every 100-200 hours of operation, depending on usage conditions (e.g., saltwater vs. freshwater).

Can I replace just the impeller instead of the whole kit?

While possible, it is highly recommended to replace the entire kit. The housing, wear plate, and seals wear out over time and can cause premature failure of a new impeller if not replaced simultaneously.

Is this a complete kit for the job?

Yes, this kit includes all the necessary components for a standard water pump service: the housing, base, impeller, plate, gaskets, seals, and guide tube as listed in the "What's in the Box" section.

What tools are needed for installation?

You will need a standard set of mechanic's tools, including socket and wrench sets, a screwdriver, a gasket scraper, and a gear lube pump. A torque wrench is recommended for proper assembly.

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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