Description

Mercury MerCruiser Quicksilver 25-31986 is a genuine Mercury Marine O-ring used as a sealing ring in select Mercury, Mariner, MerCruiser, and older sterndrive / outboard assemblies. Mercury parts references list this as 25-31986 O-RING, with manufacturer part number 31986 and GTIN / UPC 745061135390. It is a broad-use OEM sealing part best matched by the exact Mercury parts diagram callout.

Key Features

• Genuine Mercury Marine / Quicksilver O-ring reference
• OEM part number: 25-31986
• Base part reference: 31986
• GTIN / UPC reference: 745061135390
• Catalog package reference: approximately 3.50 in. x 3.50 in. x 0.75 in.
• Catalog weight reference: approximately 0.02 lb
• Aftermarket size reference: 2.635 in. / 67 mm I.D. x 0.210 in. / 5.3 mm width

Engine Compatibility

This O-ring appears in Mercury parts references across many older Mercury / Mariner outboard applications, including select 35 HP, 40 HP, 45 HP, 50 HP, 60 HP, 65 HP, 70 HP, and related 350, 400, 402, 450, 500, and 650 model-family listings depending on serial number range. Mercury where-used data also lists older MerCruiser-related applications including “0” sterndrive 1965–1966 and 60 Renault 68 I/L4 1965–1968 references.

Serial Number Fitment Notice

O-ring fitment depends on the exact engine, drive, gear housing, component group, and serial number range. Always confirm compatibility using the Mercury or MerCruiser serial number and the exact parts diagram before ordering, especially because 25-31986 appears across many different assemblies.

When This Part Needs Replacement

Replace this O-ring whenever the related assembly is opened, or if the original seal is flattened, cut, brittle, swollen, cracked, missing, or no longer sealing properly. Reusing an old compressed O-ring can lead to leaks and repeat service.

Installation Notes

Clean the O-ring groove and mating surface before installation. Lightly lubricate the O-ring with the service-manual-approved lubricant where specified, and make sure it seats evenly without twisting, stretching, pinching, or rolling during assembly. Confirm the exact diagram location before installation because this O-ring has broad Mercury and MerCruiser usage.

Alternate/Superseded Part Numbers

• 25-31986
• 31986
• Sierra 18-7160
• GLM 83340
• Mallory 9-76545
• Volvo Penta 3852866 — related cross-reference in supported applications
• OMC / Johnson / Evinrude 0508490, 0913850, 3852866 — related cross-reference references

Parts Desk Insight

This is a broad-use sealing ring, so the safest match is the exact diagram callout rather than engine horsepower alone. The size can help confirm the part, but serial number and diagram location are the most reliable way to avoid ordering the wrong O-ring.

Shipping: Ships same or next day for fast Canada wide shipping.