The Vertical Reed Block Gasket (Mercury OEM Part Number 27-657443) is a key sealing component used on many legacy Mercury 2-stroke V6 150HP and 175HP outboards equipped with vertical reed blocks. This gasket installs between the reed block assembly and the crankcase, sealing the intake path so the engine maintains proper crankcase pressure and fuel mixture control.
At Buckshot Racing #77, this gasket is supplied for owners maintaining or rebuilding classic Mercury V6 engines where proper intake sealing is essential for performance and reliability.
Designed for Mercury Vertical Reed Intake Systems
Early Mercury V6 engines used a vertical reed block intake design, where reed cages mount vertically in the crankcase. These reeds regulate the air-fuel mixture entering the crankcase during the intake cycle.
The 657443 gasket seals the reed cage to the block, preventing air leaks that can disrupt fuel delivery. When this gasket seals properly, the engine maintains stable idle quality, consistent throttle response, and proper crankcase compression. Even small intake leaks can cause lean conditions, hesitation, or poor idle performance.
Mercury Engines That Use the 657443 Reed Block Gasket
The Mercury 657443 Vertical Reed Block Gasket fits many Mercury 2-stroke V6 engines using vertical reed blocks, including numerous engines built during the late 1970s and 1980s.
Typical applications include Mercury 2.0-liter and 2.4-liter V6 outboards, such as the Mercury Marine / Mariner V-150 HP, V-175 HP, V-200HP, Mercury Black Max, and XR2 models.
These engines powered thousands of bass boats and performance hulls and remain popular today for restoration and performance builds.
The gasket is specifically designed for vertical reed block intake systems, which were standard on early Mercury V6 engines before later horizontal reed designs became common.
Cross-Reference and Replacement Part Numbers
The Mercury 27-657443 gasket corresponds with several OEM and aftermarket service numbers used across multiple production years. Common cross-reference numbers include 10-689, Sierra 18-0129, Mallory 9-60062, 30670, 508852, 516-25, 65744, 657441, 657442, and 657443.
These numbers are frequently referenced in Mercury service manuals, aftermarket repair kits, and parts catalogs when servicing vertical reed block engines.
Important During Reed Service or Engine Rebuilds
Whenever the reed blocks are removed for inspection, reed replacement, or engine rebuilding, the gasket should always be replaced. Heat cycles and compression eventually flatten gasket material, increasing the risk of vacuum leaks.
Installing a fresh gasket ensures proper crankcase pressure and reliable reed operation. This is particularly important for engines that have been rebuilt or modified, where maintaining stable airflow and fuel delivery is critical.
Contact Mike at 714-697-1716 or mike@buckshotracing77.com for technical support.
Supporting Legacy 2-Stroke Mercury V6 Outboards
Many Mercury 2.0L and 2.4L V6 engines, including the 150 HP, 175 HP, 200 HP, Black Max, and XR2, are still widely used today. It also fits the reed blocks found on the Mercury 3.4 Liter V6 250 HP and 275 HP outboards with 6 Carbs.
Maintaining these engines with the correct reed block gaskets helps preserve the performance and reliability that made these Mercury two-stroke platforms legendary. The Mercury Vertical Reed Block Gasket 657443 remains a small but essential component for keeping these classic V6 outboards running strong.
Note: Six (6) Gaskets are required to change all the reed blocks in a Mercury V6.
Contact Mike at 714-697-1716 or mike@buckshotracing77.com for technical support.