Mercury MerCruiser Double Yoke / Center Socket U-Joint Assembly 393831

The Mercury MerCruiser 393831 is a genuine OEM double yoke / center socket used in the U-joint driveline assembly on selected MerCruiser sterndrives. This component sits between the two U-joint cross-and-bearing assemblies and forms the center connection that allows the driveline to transmit power while accommodating the movement and steering articulation of the drive. One is required per U-joint assembly.

Compatible Applications

• R / MR / Alpha One Sterndrive 19831990, serial range 6225577 through 0F386995
• R / MR / Alpha One Transom Assembly 19831990, serial range 6216687 through 0F386995
• Selected Bravo, Bravo Two, and Bravo Three applications serial range varies by drive generation

Always confirm fitment using the sterndrive serial number and the applicable Mercury parts diagram. Bravo applications vary by generation and serial range.

Serial Number & Fitment Notice

Confirm the sterndrive serial number before ordering. MerCruiser used different U-joint assemblies, yokes, and center sockets across Alpha One and Bravo drive generations. Part 393831 must be matched to the specific drive parts diagram engine model and horsepower alone are not sufficient to confirm fitment. Later drives (approximately 2000 and newer) may use a larger center socket; verify the bore dimensions match your application.

Product Details

• OEM Part Number: 393831
• Also Referenced As: 39383, 39383T (earlier Mercury references)
• GTIN: 745061141179
• Function: Double yoke / center socket U-joint driveline assembly
• System: Sterndrive driveline / universal joint assembly
• Quantity Required: 1 per U-joint assembly
• Bore Diameter: 1.079 in. (for matching U-joint cross-and-bearing assemblies)

When to Replace

Inspect the double yoke whenever servicing the U-joint assembly. Replace if the yoke shows any of the following:

• Worn or damaged bearing-cap bores
• Corrosion, pitting, or rust damage
• Cracking or visible deformation
• Excessive driveline play or vibration
• Damage caused by a failed U-joint cross or bearing
• Uneven or loose fit around the bearing caps

A worn center yoke can cause repeat U-joint failures even after installing new cross-and-bearing kits if the bores are damaged, the yoke itself must be replaced.

Installation Notes

When replacing the double yoke, inspect both U-joint cross-and-bearing assemblies and the adjoining coupling and gear-end yokes at the same time. Mercury diagrams show two cross-and-bearing assemblies used with this center yoke. Ensure bearing caps seat fully and that the assembled U-joints articulate smoothly without binding or excessive looseness. Follow the appropriate Mercury MerCruiser service manual for assembly procedures, lubrication specifications, and driveline inspection intervals.

Alternate / Superseded Part Numbers

• 393831
• 39383
• 39383T

Mercury parts diagrams show 393831 as the current replacement for earlier 39383 / 39383T references.

Related Parts

• Mercury / MerCruiser U-Joint Cross & Bearing 866136A01
• Mercury / MerCruiser U-Joint Cross & Bearing 805536A2
• Mercury / MerCruiser U-Joint Cross & Bearing 75832T
• Sierra Heavy-Duty U-Joint 18-2104 MerCruiser / OMC / Volvo Penta

Parts Desk Insights

Best Use Case: This is the right part when a U-joint failure has damaged the center yoke bores not just a routine cross-and-bearing replacement. If a customer is experiencing repeat U-joint problems after installing new bearings, the double yoke is the first place to look. It’s also commonly needed during a full driveline rebuild on older Alpha One and early Bravo drives.

Common Issues: The most frequent mistake is ordering this part based on engine model or horsepower instead of confirming the sterndrive serial number. The 393831 center socket has a 1.079 in. bore later drives use a larger bore center socket that is not interchangeable. If the serial number falls outside the listed range, check the drive diagram carefully before ordering.