Sierra O-Ring 18-7157 for MerCruiser Stern Drive Model I (1963)

The Sierra 18-7157 is an O-Ring used in the stern drive assembly on MerCruiser Model I stern drives built in 1963. It seals mating surfaces within the drive unit to keep water out and lubricant in, protecting internal gearcase components from corrosion and contamination. As a direct-fit component for this specific stern drive model and year, it is intended for use during drive unit service, rebuilds, or seal replacement where the original O-ring has hardened, cracked, or lost its seal due to age and heat cycling.

This is a single O-ring, sold individually, and is identified by Sierra part number 18-7157. It is manufactured to fit the MerCruiser Model I stern drive within the serial number range 1534570 through 1684187. Installing the correct O-ring for this specific model and serial range helps ensure a proper seal and prevents water intrusion or lubricant loss in the drive unit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7157
• Item Type: O-Ring
• UPC: 808282259686
• Weight: 0.11 pounds
• Unit Count: 1 O-Ring
• Fitment: MerCruiser Stern Drive Model I (1963), serial number 1534570 thru 1684187

Fitment

• MerCruiser Stern Drive Model I, 1963, serial number range 1534570 thru 1684187

Frequently Asked Questions

What is the Sierra 18-7157 used for? The Sierra 18-7157 is an O-Ring used within the stern drive assembly on a MerCruiser Model I stern drive to seal against water intrusion and lubricant loss.

Which MerCruiser models does the 18-7157 O-Ring fit? It fits the MerCruiser Stern Drive Model I built in 1963, within the serial number range 1534570 thru 1684187.

How many O-rings come in one order? Each order of Sierra part number 18-7157 includes one O-ring.

Is the 18-7157 a genuine Sierra part or aftermarket? The 18-7157 is a Sierra-branded O-ring, identified by Sierra's own part number 18-7157.

How much does the 18-7157 O-Ring weigh? The Sierra 18-7157 O-Ring weighs 0.11 pounds.

Can I use the 18-7157 on a MerCruiser Model I outside the listed serial range? The 18-7157 is specified for MerCruiser Model I units within serial number range 1534570 thru 1684187; units outside that range are not confirmed to use this part.

What is the UPC for the Sierra 18-7157? The UPC for the Sierra 18-7157 O-Ring is 808282259686.

When would I need to replace this O-ring? This O-ring should be replaced during stern drive service or rebuild on a MerCruiser Model I, or if the existing seal has hardened, cracked, or begun leaking.

Does the 18-7157 include any other seals or gaskets? No, the 18-7157 order includes only the O-ring itself with no additional seals or gaskets.

Is the 18-7157 O-Ring model-specific or a universal size? The 18-7157 is specified by Sierra for the MerCruiser Model I stern drive rather than as a universal O-ring size.