Sierra Piston Ring 18-3972 for Johnson/Evinrude 5/6/8/7.5 HP Outboards, 1986-95, 1.937 Inch Standard Bore

The Sierra 18-3972 is a standard-bore piston ring for Johnson/Evinrude (OMC) outboard motors, engineered as a direct replacement for the factory ring set on applicable powerheads. It is sized for a 1.937 inch standard bore and is intended for use in 2-cylinder engines rated 5, 6, 8, and 7.5 horsepower for the 1986-95 model years, with the exception of 1991 60-degree V models. The ring is manufactured from alloy steel and cast iron for wear resistance and a reliable seal against the cylinder wall, helping maintain compression and reduce blow-by during a rebuild or piston service.

This is a standard-size ring, matched to the original bore diameter rather than an oversize/overbore replacement, making it the correct choice when the cylinder has not been bored out. It ships as a single unit count and is backed by Sierra's standard limited warranty, giving technicians and DIY boaters a dependable component for internal engine repair work on compatible Johnson/Evinrude powerheads.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3972
• Product Name: Piston Ring
• Item Type: Piston Rings
• Standard Bore: 1.937 inches
• Cylinder Configuration: 2-cylinder
• Ring Size: Standard
• Material: Alloy Steel, Cast Iron
• Weight: 0.03 pounds
• Included Components: Piston Rings
• Unit Count: 1
• UPC: 808282235055, 707390455778
• Warranty: Sierra Limited Warranty

Fitment

• Johnson/Evinrude (OMC) outboard, 5/6/8/7.5 HP, 2-cylinder, 1986-95, except 1991 60-degree V models

Replaces (OEM)

• OMC 390082

Frequently Asked Questions

What engines does the Sierra 18-3972 piston ring fit? It fits Johnson/Evinrude (OMC) 2-cylinder outboards rated 5, 6, 8, and 7.5 HP for the 1986-95 model years, except 1991 60-degree V models.

What bore size is this ring made for? The 18-3972 is sized for a 1.937 inch standard bore, not an oversize or bored-out cylinder.

Is the 18-3972 a standard ring or an oversize ring? It is a standard ring, matched to the factory bore diameter rather than a.020 or.030 oversize replacement.

What OEM part number does the 18-3972 replace? The Sierra 18-3972 replaces OMC part number 390082.

What is the 18-3972 ring made of? It is made of alloy steel and cast iron, materials chosen for wear resistance and a durable seal against the cylinder wall.

How many rings come in the package? The Sierra 18-3972 is sold as a single unit count of piston rings for one piston.

How much does the 18-3972 piston ring weigh? It weighs 0.03 pounds.

Will this ring work on a 1991 60-degree V model? No, the 18-3972 fitment for 5/6/8/7.5 HP 1986-95 engines specifically excludes 1991 60-degree V models.

Is the Sierra 18-3972 genuine Sierra or aftermarket? The 18-3972 is a genuine Sierra part, sold as a direct-fit replacement for the OMC piston ring on covered Johnson/Evinrude powerheads.

What is the cylinder count for engines using the 18-3972? The 18-3972 is designed for 2-cylinder Johnson/Evinrude outboards in the 5/6/8/7.5 HP range.

Does the 18-3972 come with a warranty? Yes, the Sierra 18-3972 is covered by Sierra's limited warranty.