UANOFCN Exhaust Flapper Replacement for MerCruiser 807166A1 2-Pack with Grommets — Metal-Rubber OEM Fit for 175–370 Engines

UANOFCN 807166A1 Exhaust Flapper is a direct-fit replacement shutter assembly designed to restore proper exhaust sealing and water shutter function on compatible MerCruiser stern drive 175–370 series engines.

When an exhaust flapper fails it can cause water intrusion, noise, and reduced engine performance. This replacement set from UANOFCN includes two metal-and-rubber flapper shutters plus four grommets and is engineered to match the fit and function of the original MerCruiser 807166A1 / GLM 89175 units. The parts are intended for a range of V6 and V8 MerCruiser and GM small- and big-block applications across specific model years and joint types; check fit notes carefully before ordering.

Which engines and configurations does this flapper fit?

This replacement is compatible with many MerCruiser and GM V6/V8 stern drive models that use a 3" water shutter and the referenced part number. It covers a variety of model years and both wet- and dry-joint manifolds, but it is not universal.

• Fits MerCruiser 807166A1 and GLM 89175 applications with 3" water shutter.
• Compatible with MerCruiser V6/V8 w/4" Y-pipe (1992–2001) and GM V6/V8 small-block dry joints (2002–2010) with specified angles.
• Supported engine models include 175–205 V6 (GM 229/262), 200–320 V8 small-block (GM 305/350/377), and 330–370 V8 big-block (GM 454/502) where original joints are wet.
• Not suitable for V6 one-piece manifold designs or early V8s with through-pinned flappers—use alternate part numbers in those cases.

How durable and OEM-like are these components?

The UANOFCN shutters combine metal cores with molded rubber sealing surfaces for a balance of strength and flexibility. Materials and construction aim to meet OEM dimensions and function so the shutter moves and seals like the original component.

• Metal inner structure for structural integrity under exhaust flow.
• Rubber sealing edge provides a water-tight shutter against the exhaust outlet.
• Included grommets supply proper mounting and vibration isolation.
• Manufactured to match OEM fit tolerances for straightforward installation.

What should I know about installation and fit notes?

Installation typically involves removing the old flappers and grommets, cleaning the mounting area, then pressing the new units into position with the supplied grommets. Verify the manifold joint type and year range first to avoid misfit.

• Remove exhaust assembly access panels to reach flapper area.
• Clean mating surfaces and inspect for corrosion or warped housings before installing.
• Use supplied grommets; confirm that sealing faces align and flap moves freely.
• Do not use this part on V6 engines with one-piece manifolds or early pinned V8 designs.

Who is this for: Boaters and marine technicians who need a cost-effective, OEM-dimension replacement exhaust flapper for MerCruiser and compatible GM stern drive engines. This product suits owners of mid-1990s to 2010 models with the specified joint types who want to restore proper exhaust shutter operation without buying a full manifold assembly. Confirm your engine model, joint angle, and manifold type before purchase to ensure a correct match.