Sierra 18-3982 Piston Ring Set, 3.500 Standard Bore, for Mercury 140-200 HP XR6/MAG III V-6 Outboards

The Sierra 18-3982 Piston Ring Set is a set of two piston rings sized for a 3.500 inch standard bore, built for Mercury 140-200 HP XR6/MAG III V-6 outboard engines. It is manufactured as a direct equivalent to Mercury Marine 39-822321A12, giving boat owners and marine technicians a reliable replacement option when rebuilding or servicing the powerhead on these two-ring inline piston applications. Each ring is finished with a brushed exterior surface for proper seating and wear characteristics during break-in.

Piston rings seal the combustion chamber, control oil consumption, and transfer heat from the piston to the cylinder wall, so correct bore sizing is critical to a good rebuild. This set is specified for the 3.500 inch standard bore listed for the 140-200 HP XR6/MAG III V-6 application, matching the piston (18-4635 port / 18-4636 starboard) used in that engine family. Sierra manufactures its parts to meet or exceed the specifications of the original equipment part it replaces, making the 18-3982 a straightforward drop-in for engine rebuilds, top-end overhauls, or piston ring replacement jobs on the applicable Mercury outboards.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3982
• Category: Mercury Outboard 2 Ring Inline Pistons
• Bore Size: 3.500 inches / Standard
• Rings per Set: 2
• Weight: 0.07 pounds
• Product Dimensions: 0.39 x 0.39 x 0.39 inches
• Finish: Brushed
• UPC: 808282124809

Fitment

• Mercury 140-200 HP, XR6/MAG III V-6 outboards, 3.500 inch standard bore (port and starboard piston applications)

Replaces (OEM)

• 39-822321A12

Frequently Asked Questions

What engines does the Sierra 18-3982 piston ring set fit? It fits Mercury 140-200 HP XR6/MAG III V-6 outboards with a 3.500 inch standard bore, matching both the port and starboard piston applications for that engine family.

How many rings come in the 18-3982 set? The set includes two piston rings, matching the two-ring inline piston design used on the applicable Mercury 140-200 HP XR6/MAG III V-6 outboards.

What OEM part number does the Sierra 18-3982 replace? Sierra 18-3982 is a direct equivalent to Mercury Marine part number 39-822321A12.

Is this ring set for a standard bore or an oversize bore? The 18-3982 set is sized for a 3.500 inch standard bore, not an oversize (.015 or.030) bore.

How much does the Sierra 18-3982 piston ring set weigh? It weighs 0.07 pounds.

What are the dimensions of the individual piston ring? Each ring in the 18-3982 set measures 0.39 x 0.39 x 0.39 inches.

Is Sierra 18-3982 genuine Mercury or an aftermarket part? The 18-3982 is a Sierra-branded aftermarket ring set manufactured to meet or exceed the specifications of the Mercury Marine 39-822321A12 part it replaces.

Does the 18-3982 set work with both the port and starboard pistons? Yes, the same 18-3982 ring part number is used with both the port piston (18-4635) and starboard piston (18-4636) on the 140-200 HP XR6/MAG III V-6 application.

What finish do the Sierra 18-3982 piston rings have? The rings have a brushed exterior finish.

What is the UPC for the Sierra 18-3982 piston ring set? The UPC for the Sierra 18-3982 Piston Ring Set is 808282124809.