Sierra 18-7117 O-Ring, Replaces 25-35027, for OMC Sterndrive and Cobra Stern Drives

The Sierra 18-7117 is a marine-grade rubber O-ring engineered as a direct replacement seal for select OMC Sterndrive and Cobra stern drive applications, and is also used across select Johnson/Evinrude, Mercruiser, and Mercury Marine engines. It measures 1.046 inches (26.6mm) in inside diameter with a 0.135 inch (3.4mm) width, sized to seat correctly in the original bore and provide a reliable fluid seal at its mounting location. The O-ring is molded from rubber for resistance to the fuel, oil, and water exposure common in sterndrive and outboard drive components, helping prevent leaks and drips at gasket and housing joints. Each package contains one O-ring, so buyers can order the exact quantity needed for a single repair without paying for a larger multi-pack. As a Sierra part, the 18-7117 is built to meet or exceed the specifications of the original equipment part it replaces, making it a straightforward drop-in choice when resealing sterndrive housings or related components. It carries the manufacturer's O.E. Cross-reference number 25-35027, so it can be matched confidently against the original part being replaced. This O-ring is a small, low-cost component, but a proper fit and quality rubber compound are essential to preventing seal failure and fluid leakage in marine drive systems.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7117
• Material: Rubber
• Inside Diameter: 1.046 inches (26.6mm)
• Width: 0.135 inches (3.4mm)
• Unit Count: 1 O-ring per package
• Weight: 0.01 pounds
• OEM Cross Reference: 25-35027

Fitment

Designed for use in select OMC Sterndrive and Cobra stern drive applications, and also used in select Johnson/Evinrude, Mercruiser, and Mercury Marine engines.

Replaces (OEM)

• 25-35027

Frequently Asked Questions

What is the inside diameter and width of the Sierra 18-7117 O-ring? The Sierra 18-7117 has a 1.046 inch (26.6mm) inside diameter and a 0.135 inch (3.4mm) width.

What does the Sierra 18-7117 O-ring replace? It replaces OEM part number 25-35027, and is engineered as a direct-fit substitute for that original seal.

What engines and drives is the 18-7117 O-ring used on? This O-ring is used in select OMC Sterndrive and Cobra stern drive applications, and also fits select Johnson/Evinrude, Mercruiser, and Mercury Marine engines.

How many O-rings come in a package? Each package of the Sierra 18-7117 contains one O-ring.

What material is the 18-7117 O-ring made from? It is molded from rubber, suited to sealing against fuel, oil, and water exposure in marine drive components.

Is the Sierra 18-7117 a genuine OEM part or an aftermarket replacement? The 18-7117 is a Sierra aftermarket replacement O-ring built to meet or exceed the specifications of the original 25-35027 part it replaces.

How much does the 18-7117 O-ring weigh? The Sierra 18-7117 O-ring weighs 0.01 pounds.

Can I use the 18-7117 O-ring on a Mercury Marine drive? Yes, the 18-7117 is used in select Mercury Marine engines in addition to OMC Sterndrive, Cobra, Johnson/Evinrude, and Mercruiser applications.

How do I confirm the Sierra 18-7117 is the correct O-ring for my repair? Match it against the O.E. Number 25-35027 on your original part, or confirm your engine or drive is one of the OMC Sterndrive, Cobra, Johnson/Evinrude, Mercruiser, or Mercury Marine applications this O-ring is designed for.

Where is the 18-7117 O-ring typically installed? It is used as a sealing O-ring within OMC Sterndrive and Cobra stern drive housings and related components on the compatible engines listed for this part.