Upper Unit Seal Kit – Fits MerCruiser Alpha One Gen I, R, MR, MC-1 (Replaces 26-32511A1, 18-2648)

Product Details

This Upper Unit Seal Kit is designed for MerCruiser Alpha One Gen I, R, MR, and MC-1 sterndrive upper units. It delivers reliable sealing performance for a broad range of MerCruiser models including 1A, 1B, 1C, and EZ Shift configurations, ensuring proper protection against water intrusion and fluid leakage.

This aftermarket kit directly replaces Mercury Marine/Quicksilver part number 26-32511A1, as well as GLM 87500 and Sierra Marine 18-2648.

• Complete seal replacement for upper unit maintenance and rebuild
• Compatible with MerCruiser sterndrive Alpha One Gen I series
• Engineered to OEM specifications for secure fitment and durability

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Technical Specs

Application

MerCruiser sterndrive upper units

OEM Replacement

26-32511A1

Part Type

Seal kit

Unit

Upper unit

What's in the Box

• Complete upper unit seal kit with all required gaskets and seals

Installation Notes

1. Disconnect battery and remove upper unit from lower unit per manufacturer service manual.
2. Drain all lubricant from the upper gearcase and inspect for metal debris or contamination.
3. Remove old seals and gaskets carefully, cleaning all mating surfaces thoroughly with solvent.
4. Inspect shafts, bearings, and housings for wear or damage; replace components as needed.
5. Install new seals using the appropriate seal driver or socket to avoid cocking or damage.
6. Lubricate seal lips lightly with gear oil before assembly.
7. Reassemble upper unit, ensuring all fasteners are torqued to specification.
8. Refill with manufacturer-recommended sterndrive gear lubricant to proper level.
9. Reinstall upper unit onto lower unit and verify smooth engagement.
10. Run engine in neutral and check for leaks around all seal areas.
11. Test shift operation and perform a water trial under normal operating conditions.

Troubleshooting & FAQ

How do I know if my upper unit seals need replacement?

Signs include visible gear oil leaking from the upper unit, milky or contaminated gear oil indicating water intrusion, or unusual noise during operation. Regular inspection during seasonal maintenance is recommended.

Will this kit fit both R and MR drive models?

Yes, this seal kit is engineered to fit MerCruiser R, MR, MC-1, and Alpha One Gen I upper units. Always verify your drive serial number and model designation before ordering.

Do I need special tools to install this seal kit?

A seal driver set, torque wrench, and basic hand tools are recommended. Some seals may require a press or appropriately sized socket for safe installation without damage.

Can I reuse the old seals if they look okay?

No. Seals are designed for single use and lose their sealing capability once removed. Always replace with new seals during any upper unit service to prevent leaks.

What type of gear oil should I use after installing the seal kit?

Use Mercury/Quicksilver Premium or High Performance gear lubricant as specified in your owner's manual. Capacity and viscosity vary by model, so consult your service documentation.

How often should upper unit seals be replaced?

Replace seals whenever the upper unit is disassembled for service, or if leaks or contamination are detected. Typical service intervals range from 100–300 hours depending on operating conditions.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

• Verify images/specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.