Sierra 18-2533 Transom Seal for OMC Sterndrive and Cobra Stern Drive, Replaces 911797

The Sierra 18-2533 Transom Seal is a round transom seal engineered for OMC Sterndrive and Cobra Stern Drive applications. It seals the transom opening where the drive unit passes through the boat's hull, forming a critical barrier against water intrusion into the bilge. Each package contains one transom seal, sized and molded to seat directly in place of the original equipment seal it replaces.

Sierra builds this seal to meet or exceed the specification of the original OMC part, giving boat owners a direct-fit replacement without modification. It is commonly needed when the factory transom seal has hardened, cracked, or begun to leak with age, a routine maintenance item for stern drive boats. The 18-2533 is backed by a limited warranty and is cross-referenced to OMC part number 911797, making it easy to identify as the correct replacement for that original component.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2533
• Product Type: Transom Seal
• Shape: Round
• Fits: OMC Sterndrive, Cobra Stern Drive
• Package Quantity: 1 transom seal per package
• Weight: 0.13 pounds
• UPC: 030999312280
• GTIN: 00030999312280
• Warranty: Limited Warranty

Fitment

Designed for OMC Sterndrive and Cobra Stern Drive units.

Replaces (OEM)

• OMC 911797

Frequently Asked Questions

What does the Sierra 18-2533 transom seal fit? The Sierra 18-2533 is designed for OMC Sterndrive and Cobra Stern Drive applications, sealing the transom opening where the drive unit passes through the hull.

Is the Sierra 18-2533 the same as OMC part 911797? Yes, the 18-2533 transom seal is the direct cross-reference replacement for OMC 911797.

How many seals come in a package of the 18-2533? One transom seal is included per package of the Sierra 18-2533.

How much does the 18-2533 transom seal weigh? The Sierra 18-2533 transom seal weighs 0.13 pounds.

What shape is the 18-2533 transom seal? It is a round transom seal, matching the shape of the OMC 911797 seal it replaces.

Is the Sierra 18-2533 a genuine OEM part or an aftermarket equivalent? The 18-2533 is a Sierra-manufactured replacement part built to meet or exceed the original equipment part it replaces, not an OEM-branded component.

Does the 18-2533 come with a warranty? Yes, the Sierra 18-2533 transom seal is covered by a limited warranty.

How is the 18-2533 different from Sierra's 18-2767 and 18-2768 transom seals? The 18-2533 is a distinct transom seal for OMC Sterndrive and Cobra Stern Drive units, while the 16-hole 18-2767 replaces OMC 313080 for 120 HP and up applications from 1967-77, and the 22-hole 18-2768 replaces OMC 909527 for all applications from 1978-86 -- these are separate parts for different fitments, so match the part number to your drive.

What does a transom seal like the 18-2533 do? A transom seal such as the Sierra 18-2533 seals the opening in the boat's transom where the stern drive unit passes through, preventing water from entering the bilge.

What is the UPC for the Sierra 18-2533 transom seal? The Sierra 18-2533 transom seal carries UPC 030999312280.