Sierra Engine Coupler 18-21751, Replaces 3853962-3, Fits 2.5L, 3.0L, 4.3L, 5.0L, 5.7L, 7.4L, 8.2L Engines

The Sierra 18-21751 Engine Coupler connects the engine flywheel to the drive unit on stern drive powered boats, transferring rotational power from the engine to the outdrive while allowing for the flex needed to accommodate engine and drive alignment. It is built from metal with a machined finish for durability under continuous torque loading, and is finished in white. This coupler is a direct replacement for OEM number 3853962-3, making it a straightforward swap when the original coupler wears out, cracks, or fails to properly transmit power between the engine and drive. It fits a range of stern drive engine displacements including 2.5L (1986), 3.0L (1986-90), 4.3L, 5.0L, 5.7L (1986), 7.4L (1990-98), and 8.2L (1992-93, 1998), with the 4.3L application limited to KW and KWB suffix engines only. Replacing a worn engine coupler is a common maintenance task when a boat develops vibration, clunking on shift, or difficulty engaging gear, since a deteriorated coupler can no longer properly transfer engine power to the outdrive. Each unit ships as a single piece.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-21751
• Material: Metal
• Color: White
• Exterior Finish: Machined
• Thread Size: 3/8 Inch
• Thread Type: NPT
• Connector Type: Coupling
• Weight: 6.45 pounds
• Country of Origin: Taiwan
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• Number of Pieces: 1

Fitment

• 2.5L (1986)
• 3.0L (1986-90)
• 4.3L (KW and KWB suffix only)
• 5.0L
• 5.7L (1986)
• 7.4L (1990-98)
• 8.2L (1992-93, 1998)

Replaces (OEM)

• 3853962-3

Frequently Asked Questions

What does the Sierra 18-21751 engine coupler do? The Sierra 18-21751 engine coupler connects the engine flywheel to the stern drive unit, transmitting engine power to the outdrive while flexing slightly to accommodate alignment between the two.

Is the 18-21751 a direct replacement for OEM part 3853962-3? Yes, Sierra 18-21751 replaces OEM number 3853962-3 and installs as a direct equivalent for that application.

What engines does the 18-21751 coupler fit? Coverage includes 2.5L (1986), 3.0L (1986-90), 4.3L (KW and KWB suffix engines only), 5.0L, 5.7L (1986), 7.4L (1990-98), and 8.2L (1992-93, 1998) stern drive engines.

Does the 4.3L application fit all 4.3L engines? No, the 4.3L fitment for the 18-21751 coupler is limited specifically to engines with the KW or KWB suffix, not all 4.3L blocks.

What material is the 18-21751 engine coupler made from? It is made from metal with a machined finish, providing the rigidity needed to handle continuous torque transfer between engine and drive.

How much does the 18-21751 engine coupler weigh? The Sierra 18-21751 engine coupler weighs 6.45 pounds.

How many couplers come in a package? The Sierra 18-21751 ships as a single piece.

What color is the 18-21751 coupler? It has a white finish.

What are the signs that an engine coupler needs to be replaced? Vibration, a clunking noise when shifting into gear, or reduced power transfer to the drive are common symptoms of a worn coupler, and the 18-21751 addresses these on applicable engines.

Where is the 18-21751 engine coupler manufactured? The country of origin for the Sierra 18-21751 engine coupler is Taiwan.

Is the 18-21751 an OEM part or aftermarket? It is a Sierra aftermarket part manufactured to replace OEM number 3853962-3 for the listed engine applications.