Water Shutter Assembly – Fits MerCruiser V6/V8 Engines (Replaces 807166A1, 807166A2)

Water Shutter Assembly – Fits MerCruiser V6/V8 Engines (Replaces 807166A1, 807166A2)

This water shutter assembly is designed for MerCruiser V6 and V8 sterndrive engines from 1996 to the present, including 4.3L (262 CID), 5.0L (305 CID), and 5.7L (350 CID) models equipped with a two-piece exhaust manifold.

This component is a direct replacement for MerCruiser part numbers 807166A1, 807166A2, and the 807166A3 kit. It serves the critical function of preventing water from flowing back into the engine through the exhaust system, which can cause severe damage like engine hydrolock.

• Installation Location: Mounts inside the exhaust Y-Pipe.
• Engine Compatibility: Fits gasoline MerCruiser V6 & V8 engines (1996+).
• Complete Kit: Includes the water shutter and two required grommets for a drop-in installation.

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 Shutter Assembly (Replaces 807166A1/807166A2)
• 2 x Grommets (Replaces 25-8M0204688)

Installation Guide

1. Safety First: Disconnect the boat's battery before beginning work on the engine or exhaust systems.
2. Access the Y-Pipe: Locate and access the exhaust Y-pipe where the upper exhaust hoses connect. This may require removing other components.
3. Remove Old Shutter: Carefully remove the old, failed water shutter and its grommets from within the Y-pipe.
4. Clean the Surface: Thoroughly clean the mounting surfaces inside the Y-pipe to ensure a proper seal for the new grommets.
5. Install New Grommets: Insert the two new grommets into the designated holes inside the Y-pipe.
6. Install New Shutter: Carefully insert the pins of the new water shutter assembly into the grommets until it is securely seated.
7. Verify Function: Ensure the shutter can swing open and closed freely without binding.
8. Reassemble Exhaust: Reconnect any exhaust hoses or components that were removed for access.
9. Final Check: Reconnect the battery. Start the engine and check for any exhaust or water leaks around the service area.

Troubleshooting & FAQ

How do I know if I need to replace my water shutter?

Common signs of a failed water shutter include a rattling noise from the exhaust, evidence of water in the engine oil, engine overheating, or difficulty starting. The most critical sign is finding water in the cylinders, which indicates engine hydrolock, a severe condition that a functioning shutter helps prevent.

What is the purpose of a water shutter?

It acts as a one-way valve located in your exhaust Y-pipe. It opens to let exhaust gases out when the engine is running and closes to prevent water from flowing back into the engine cylinders when the engine is off or when decelerating quickly.

What engines does this water shutter assembly fit?

It is designed for a wide range of MerCruiser V6 and V8 engines made from 1996 and onward, specifically those with "Gen+" (Generation Plus) architecture and a two-piece exhaust manifold. Always confirm your engine model and year before ordering.

Is this a single part or a complete kit?

This is a complete replacement assembly that includes one water shutter and a pair of new grommets required for a proper installation. This corresponds to what MerCruiser sells as kit 807166A3.

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.