UANOFCN Exhaust Flapper for MerCruiser 807166A1 — 3" Water Shutter Kit, 2 Flappers with 4 Grommets

The UANOFCN 807166A1 Exhaust Flapper is a direct-fit replacement shutter assembly designed to restore correct exhaust flow on compatible MerCruiser stern drive V6 and V8 engines.

This kit includes two metal-rubber flapper shutters and four grommets engineered to match the dimensions and mounting pattern of MerCruiser part 807166A1 (also cross-referenced to GLM 89175). It’s built for a range of MerCruiser models and model-year joint configurations used across 175–370 engine families, giving boat owners a durable OEM-quality option when the original flappers wear, crack, or stick.

Which MerCruiser engines and joints will this flapper fit?

This 3" water shutter is compatible with many MerCruiser V6 and V8 stern drive configurations from the early 1980s through 2010, including both wet- and dry-joint installations where the flange and angle match the listed specifications. It does not fit some one-piece manifold V6s or early V8s that use a round pin through the flapper.

• Fits model families: 175–205 (V6), 200–320 (V8 S.B.), 330–370 (V8 B.B.).
• Compatible with MerCruiser 807166A1 and GLM 89175 reference numbers.
• Works with 1992–2001 V6/V8 w/4" Y-pipe and select 2002–2010 GM S.B. dry-joint angles (7° and 14°).
• Not for one-piece manifold V6s or early V8s using pin-through design.

How durable and reliable is the UANOFCN flapper assembly?

UANOFCN manufactures the shutters using premium metal and rubber compounds chosen for wear resistance and flexibility in marine exhaust environments. The design aims to resist corrosion, maintain sealing under pressure, and tolerate repeated thermal cycling typical of stern drive exhaust systems.

• Metal-reinforced body for shape retention and impact resistance.
• Rubber sealing surfaces engineered for resilience and water-tight closure.
• OEM-quality fit intended for straightforward replacement without modification.
• Includes replacement grommets to secure a snug mount and reduce vibration wear.

Can I install this flapper myself and what comes in the kit?

The kit ships with two exhaust flapper shutters and four installation grommets, allowing you to swap both sides or keep a spare on hand. Basic mechanical skills and common hand tools are usually sufficient for the job; installation steps depend on your stern drive configuration and may require access under the transom or removal of the exhaust elbow.

• Kit contents: 2 flapper shutters + 4 grommets (installation hardware not included).
• Recommended tools: socket set, screwdrivers, penetrating lubricant, and marine-grade sealant where applicable.
• Installation note: confirm your manifold/joint type before ordering to avoid mismatches.
• Professional service recommended if you’re unfamiliar with stern drive exhaust disassembly.

Will this part perform like the original MerCruiser component?

UANOFCN’s 807166A1 is produced to match the form, fit, and function expected of the factory shutter it replaces, offering a cost-effective alternative while aiming to preserve proper exhaust routing and backpressure characteristics. Performance depends on correct fitment and proper installation, so verify part compatibility with your engine serial and configuration.

• Engineered to OEM dimensions for correct sealing and movement.
• Helps restore exhaust shutter operation when originals are degraded.
• Not a universal item—ensure exact model and joint compatibility first.
• Keeping spare grommets supplied reduces future maintenance downtime.

Who is this for: Boat owners, mechanics, and marinas that service MerCruiser stern drive engines from the 175–370 families who need a reliable replacement shutter assembly. If your engine uses the matching 3" water shutter pattern and you’re replacing worn or damaged flappers, this UANOFCN kit provides durable components ready for installation. Confirm your manifold style and year-range before purchase to ensure fitment; if your engine originally had a one-piece manifold or a pin-through flapper, choose the appropriate alternative part.