Water Distribution Housing – Fits Mercury MerCruiser 4.3L–6.2L MPI Engines (Replaces 863802T2)

Water Distribution Housing for Mercury MerCruiser 4.3L–6.2L MPI Engines

This water distribution housing is engineered for a wide range of Mercury MerCruiser MPI engines, from 4.3L to 6.2L models (1998–present). It serves as a direct, reliable replacement for original equipment, ensuring proper coolant flow in air-actuated, closed cooling systems.

This component is a direct replacement for Mercury OEM part numbers: 863802T2, 863444T2, 863631T1, and 863444T1.

• Installation Type: Direct replacement for the OEM part.
• Connection: Designed for air-actuated systems with standard hose fittings.
• Material: Constructed from a durable aluminum alloy with high-grade plastic components.

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 Distribution Housing Assembly (Replaces OEM Part 863802T2)

Explosion Diagram

Installation Guide

1. Safety First: Disconnect the boat's battery before beginning work.
2. Drain Coolant: Fully drain the engine's closed cooling system to prevent spills.
3. Disconnect Hoses: Carefully label and disconnect all hoses attached to the existing water distribution housing.
4. Remove Old Housing: Unbolt and remove the old housing assembly. Note the position of any brackets or fittings.
5. Clean Surface: Thoroughly clean the engine mounting surface to ensure a perfect seal.
6. Install New Housing: Mount the new housing assembly and tighten the bolts to the manufacturer's specified torque.
7. Reconnect Hoses: Securely reattach all cooling hoses to their correct fittings on the new housing.
8. Refill System: Refill the cooling system with the appropriate coolant mixture.
9. Final Checks: Reconnect the battery. Start the engine and carefully check for any leaks around the housing and hose connections.

Troubleshooting & FAQ

How do I confirm this fits my engine?
This housing fits a wide range of MerCruiser MPI engines from 1998 to present, including 4.3L, 5.0L, 5.7L, 6.2L, 350 MAG, and 377 MAG models. The most reliable method is to match your engine's model and serial number to the ranges listed in the ""Compatible Engine Models"" table above.

What is the difference between air-actuated and manual draining?
This housing is designed for modern air-actuated draining systems, which use air pressure to clear water for winterization. It also includes manual drain plugs, providing a reliable and flexible backup for maintenance or in case the air system is not used.

What are the signs that my current water distribution housing is failing?
Common signs of failure include visible coolant leaks from the housing body or fittings, engine overheating alarms, steam from the engine compartment, or noticeable cracks and corrosion on the unit itself.

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.