PAIR 807166A1 Exhaust Water Shutter Fits MerCruiser V6 & V8 4" Y-Pipe Set of 2

This is an aftermarket exhaust water valve poppet shutter (also called exhaust flapper or water flapper) that replaces OEM 807166A1. It installs inside the 4 inch Y-pipe on compatible MerCruiser sterndrive applications to prevent water from flowing back into the exhaust system and engine when the boat is off plane, decelerating, or facing a following sea.

Ships as one pair (2 shutters) — covers both sides of the Y-pipe. For a single shutter, see GHMarine 17ST002. V6/V8 Y-pipes typically use two shutters (one per side).

Why this part matters

A missing or damaged exhaust shutter is not just a noise issue. Water flowing back through the exhaust into the cylinders can cause hydro-lock — bending connecting rods and destroying the engine. Replacing a $70 shutter is far cheaper than a thousand-dollar engine rebuild.

Signs yours is due

·       Ticking or clacking noise from the Y-pipe area at idle — the rubber has worn off and only the metal hinge pin remains, rattling inside the pipe.

·       Engine overheating event — heat melts the rubber shutter; fragments can lodge in the Y-pipe and wear through the wall, causing water intrusion into the bilge.

·       Exhaust louder than normal — exhaust coming out of idle ports instead of prop (shutter debris blocking the exhaust path).

·       Found shutter fragments in the bellows or lower unit during routine service — inspect Y-pipe with a borescope before reassembly.

·       Routine transom service — replace every 3–5 years or whenever the drive is already off. A $70 shutter vs a thousand-dollar engine rebuild.

Will it fit my drive?

This exhaust water shutter is Compatible with MerCruiser V6 & V8 engines with a 4 inch Y-pipe and two-piece exhaust manifolds (approximately 1996–2001). Engine horsepower alone does not prove fit — match your drive serial number and Y-pipe grommet hole type.

Brand	Model / Drive	Rated HP	Stroke	Years	OEM Part No.
MerCruiser	V6 & V8 · 4in Y-pipe · 2-piece manifolds	175–400+	4-Stroke	1996–2001	807166A1
MerCruiser	V6 & V8 · 2-piece manifolds (continued)	175–400+	4-Stroke	1995–current	807166A1

 

OEM & swap numbers

Primary OEM is 807166A1 (2.48 in cross pin, square grommets). Common interchange refs: 65167, 89175, REC807166A1.

Type	Brand	Part Number	Notes
OEM	Mercury / Quicksilver	807166A1	Primary OEM · 2.48 in cross pin · square grommets
Aftermarket	PROmarine	65167	1:1 direct replacement · 4in Y-pipe 1992-2001
Aftermarket	PROmarine	65167P	Packaged line · same cross-ref 807166A1
Aftermarket	GLM	89175	1:1 direct replacement
Aftermarket	Recmar	REC807166A1	4in 1992+ / 4.5L MPI

 

Wrong part? Read before you order

·       NOT for 4.3L V6 one-piece manifold (batwing) — uses 807166A2 (2.98 in cross pin); see GHMarine 17ST007.

·       NOT for offset plate / Center Rise style (1982–1996) — uses 807166A3 (round grommet holes); see GHMarine 17ST004 / 17ST005.

·       NOT for 3 inch Y-pipe (1982–1987) — uses 99370A2; see GHMarine 17ST006.

·       NOT for 4-cyl / jackshaft engines — uses 60930; see GHMarine 17ST001.

·       NOT for drain plug WH2952 — different part entirely.

How to identify your correct shutter — check Y-pipe grommet holes

·       Rectangular holes → you need 807166A1 (this part)

·       Round holes → you need 807166A3 (different SKU 17ST004/005)

·       Y-pipe changes size below the shutter → one-piece V6 batwing manifold, you need 807166A2 (17ST007)

Cross pin diameters are NOT interchangeable: A1 = 2.48 in, A2 = 2.98 in, A3 = 2.5 in.

What ships in the box

·       2 × Exhaust water shutters (one pair) — covers both sides of the Y-pipe. For a single, see 17ST002.

·       Grommets as shown in product photos

·       Not included: hose clamps (reuse existing), adhesive (not needed for shutter), tools

Installation overview

The exhaust water shutter is NOT a bellow — no bellows adhesive or expander tool is needed. Installation is simpler than bellow replacement.

1. Remove the exhaust hose clamp at the top of the Y-pipe and pull back the rubber exhaust hose.

2. Reach in and remove the old shutter — check for fragments that may have fallen into the Y-pipe (use a borescope if needed).

3. Install the new shutter with grommets seated in the rectangular holes of the Y-pipe.

4. Reconnect the exhaust hose and clamp. Run on muffs and check for exhaust leaks.

Most applications do NOT require engine removal — the shutter is accessible from the top of the Y-pipe. Tight engine compartments may require pulling the riser or elbow for access.

Often replaced together

·       Exhaust bellow (bell housing) — GH SKU 17B1003 (ref 8M0124227 / 18654A1 family).

·       U-joint bellow — GH SKU 17B1004 (Gen I) or 17B1007 (Gen II).

·       Shift cable bellow — GH SKU 17B1005 (ref 74639A2).

·       Transom repair kit — GH SKU 17B3005 (Gen I) / 17B3007 (Gen II) / 18B5001 (Bravo).

FAQ

Will this fit my MerCruiser sterndrive?

This replaces OEM 807166A1 on MerCruiser V6 & V8 engines with a 4 inch Y-pipe and two-piece exhaust manifolds (approximately 1996–2001). Check your Y-pipe grommet holes: rectangular = A1 (this part), round = A3 (different part). Match your drive serial number before ordering.

Is this a pair or a single?

This listing is for a pair of shutters (2 pieces). For a single, see GHMarine 17ST002. V6/V8 Y-pipes typically use two shutters (one per side) — this pair covers both sides in one purchase.

Do I need to remove the engine to replace the shutter?

Most applications: no. The shutter is accessible from the top of the Y-pipe after removing the exhaust hose clamp and pulling back the hose. Tight engine compartments may require removing the riser or elbow for access. Use a borescope to check for debris before reassembly.

Can I run without the shutter?

Some boaters omit them, and some dealers say they are unnecessary. However, a single following wave or hard deceleration can push water back through the exhaust into the cylinders, causing hydro-lock and engine failure. For under $70, a replacement shutter is cheap insurance against a thousand-dollar engine rebuild.

My engine overheated — should I check the shutter?

Yes. Engine overheating melts the rubber shutter. After any overheating event, inspect the Y-pipe for shutter fragments. Fragments can block exhaust flow and even wear through the Y-pipe wall causing water intrusion into the bilge.

I hear a ticking noise from the back of the engine — is it the shutter?

A ticking or clacking sound from the Y-pipe area at idle often means the rubber has worn off and only the metal hinge pin remains. Inspect and replace before the metal hinge wears through the Y-pipe wall.

How is this different from 807166A2 or 807166A3?

A1 (this part) has a 2.48 in cross pin and rectangular grommets — for two-piece manifold V6/V8 with 4 inch Y-pipe (1996+). A2 has a 2.98 in cross pin — for one-piece V6 batwing manifolds. A3 uses round grommets — for older offset-plate / Center Rise style (1982–1996). The three are NOT interchangeable.

Please note

Aftermarket replacement part. Not affiliated with engine manufacturers named above. "Compatible with", "Replaces", and cross-ref numbers mean this part is built to work like the originals listed — always confirm fit with your drive serial number and Y-pipe grommet hole type before ordering.