Water Pump Kit - Fits MerCruiser Alpha, Bravo & TRS (Replaces 46-807151A14, 807151A7)

Water Pump Kit – Fits MerCruiser Alpha, Bravo & TRS (Replaces 46-807151A14)

This Sierra 18-3150 water pump kit is a complete assembly designed for MerCruiser engines equipped with a plastic, one-piece body sea water pump. It is engineered to fit MerCruiser Alpha (FWC), Bravo I/II/III, and TRS sterndrives, as well as various inboard marine engine models.

This assembly provides a direct replacement for MerCruiser part numbers 46-807151A14 and 46-807151A7. It serves as a comprehensive solution for replacing the entire sea water pump housing and impeller, and can also be used to upgrade older 2-piece housing pumps to the modern, reliable 1-piece design.

• Includes a complete pump housing, impeller, wear plate, O-rings, and all necessary hardware for installation.
• Compatible with freshwater cooling (FWC) systems on Alpha drives and all Bravo/TRS sterndrives.
• Features a durable one-piece plastic housing that resists corrosion and simplifies service.

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 Assembly (Replaces 46-807151A1)
• 1 x Impeller (Replaces 47-59362T1)
• 1 x Wear Plate Outer (Replaces 94576/8M0204674)
• 1 x O-Ring (Replaces 25-33465/25-8M0214925)
• 1 x Quad Ring (Replaces 25-94288/25-8M0215007)
• 5 x Screw Hex Head .312-18 x 3.250 (Replaces 10-74191/8M0204669)
• 2 x Screw Hex Head .312-18 x 2.68 (Replaces 10-807356)
• 5 x Washer (.344 x .688 x .065) Stainless Steel (Replaces 12-814806)

Installation Guide

1. Safety First: Disconnect the battery and ensure the engine is cool to the touch.
2. Drain System: Place a catch pan under the pump and drain the sea water cooling system by loosening the appropriate drain plugs.
3. Access the Pump: Loosen the serpentine belt and remove any components obstructing access to the sea water pump.
4. Remove Hoses: Carefully disconnect the inlet and outlet water hoses from the pump housing. Note their orientation.
5. Unbolt Old Pump: Remove the mounting bolts securing the old pump assembly to the engine bracket.
6. Clean Surface: Thoroughly clean the mounting surface on the engine bracket, removing any old gasket material or corrosion.
7. Install New Pump: Mount the new water pump assembly, ensuring it is correctly aligned. Hand-tighten the new bolts provided in the kit.
8. Torque Bolts: Tighten the mounting bolts to the manufacturer's specified torque sequence and value.
9. Reconnect Hoses: Re-attach the water hoses to the new pump and secure them with clamps. Re-tension the serpentine belt.
10. Refill & Check: Close all drain plugs. Reconnect the battery. Refill the cooling system according to your engine's manual.
11. Final Inspection: Start the engine and let it run for several minutes, carefully checking the pump and hose connections for any water leaks.

Troubleshooting & FAQ

How do I confirm this fits my engine?
This kit is designed for specific MerCruiser engines using a one-piece plastic sea water pump, primarily Alpha (FWC models only), Bravo, and TRS sterndrives. The best way to confirm fitment is to match your original part number to one listed in our cross-reference table (46-807151A14, 46-807151A7). Please also consult our compatible models list and use the Mercury guides linked above to verify your engine details.

Can I use this 1-piece plastic housing to replace my older 2-piece metal housing?
Yes, this one-piece plastic housing assembly is the direct successor and can be used to upgrade older, two-piece brass or plastic sea water pump bodies. This kit includes all necessary components for the conversion.

What are the signs of a failing water pump?
Common signs include the engine overheating at idle or low speeds, a noticeable drop in water pressure from the tell-tale outlet, visible water leaks from the pump housing, or a damaged/brittle impeller found during inspection. A high-pitched whining sound from the pump area can also indicate bearing failure.

How often should I replace the water pump or impeller?
For preventative maintenance, it is recommended to inspect the impeller annually and replace it every 1-2 years, depending on usage (especially in saltwater or high-debris environments). The entire housing should be replaced if you see cracks, warping from overheating, or significant scoring on the internal surfaces.

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.