Upper Gear Housing Seal Kit for MerCruiser R, MR & Alpha One Drives — Replaces Mercury 26-32511A1 and Sierra 18-2648

Product Details

This Upper Gear Housing Seal Kit is designed to reseal the drive-shaft housing on selected MerCruiser stern drives, helping prevent gear-lube leaks and water intrusion around the upper gear housing. Catalog references identify this seal-kit application for MerCruiser R, MR, and Alpha One drives, including earlier #1 drive applications.

The kit replaces Mercury Marine OEM part number 26-32511A1 and corresponds to Sierra part number 18-2648. GLM catalog information identifies the equivalent drive-shaft housing seal kit as GLM 87500 for R, MR, and Alpha One applications.

• Replacement seal kit for the upper drive-shaft housing.
• Helps restore sealing at service points in the upper gear housing.
• Direct-replacement application when the listed model and serial conditions match.
• Inspect the original components and verify the drive serial number before ordering.

Part Number Matrix

Use the following references to compare the listed replacement part with catalog numbers from other manufacturers.

Engine & Model Compatibility

Fitment depends on the drive model, production year, and serial-number range. The application information below is consolidated from the available drive-shaft housing seal-kit catalog data. Confirm the serial number on the drive before installation.

Important: Alpha One Gen II applications use a different seal-kit reference and are not included in this listing. Do not use this kit for Alpha One Gen II drives unless the original part and serial-number documentation specifically confirms compatibility.

Technical Specs

Product Type

Upper drive-shaft housing seal kit

Application

MerCruiser R, MR, and Alpha One drive-shaft housings within the listed conditions

Replacement OEM Reference

Mercury Marine 26-32511A1

Aftermarket References

Sierra 18-2648; GLM 87500

Installation

Replacement installation; access to the upper gear housing is required

Material

Sealing components; exact material composition is not specified

Warranty

Refer to the applicable seller warranty and return policy

What’s in the Box

This listing is supplied as an upper gear housing seal kit. Component styles and markings may vary by production batch. The commonly listed kit contents are:

• 1 x Grommet, reference 26-38970
• 1 x Gasket, reference 27-55810-1
• 2 x Gasket, reference 12-19183-3
• 1 x O-ring, reference 25-55801
• 1 x O-ring, reference 25-32546
• 1 x O-ring, reference 25-25439
• 1 x O-ring, reference 25-70937
• 1 x Oil seal, reference 26-32511
• 1 x Oil seal, reference 26-823894
• 1 x Oil seal, reference 26-96503-1
• 1 x Seal, reference 26-45577-1
• 1 x Grommet, reference 26-36557

Compare the supplied components with the parts being removed before final assembly. Do not assume that a component reference printed on an individual seal is the kit part number.

Installation Notes

1. Drain the gear lubricant from the stern drive completely.
2. Remove the upper gear housing assembly according to the applicable service procedure.
3. Disassemble the housing as needed to access the seals, gaskets, O-rings, and grommets. Record the orientation and position of each removed component.
4. Clean all mating surfaces and remove old sealant, debris, and corrosion without damaging the sealing surfaces.
5. Install the replacement components in the same locations and orientations as the original parts. Use only lubricant or sealant specified by the applicable service manual.
6. Reassemble the upper gear housing and tighten fasteners to the manufacturer’s service specifications.
7. Refill the drive with the correct marine gear lubricant, then perform a leak check before returning the boat to service.

Troubleshooting & FAQ

Safety & Important Information

• Verify the drive model, year, and serial number before ordering.
• Do not rely on model name alone; similar MerCruiser drives may use different seal kits.
• Do not use this listing as confirmation for Alpha One Gen II applications.
• Use the correct service procedures, tools, torque values, lubricant, and sealant for the drive being serviced.
• Professional installation is recommended when disassembly of the upper gear housing is required.

About Sea Sierra

• Marine replacement parts selected for practical service and repair applications.
• Clear part-number references to help compare aftermarket replacements with original components.
• Support focused on accurate identification and dependable fitment information.