Lower Gearcase Seal Kit – Fits MerCruiser Alpha One Gen 2 (Replaces 26-816575A3, 26-816575A1)
Lower Gearcase Seal Kit – Fits MerCruiser Alpha One Gen 2 (Replaces 26-816575A3, 26-816575A1) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Lower Gearcase Seal Kit – Fits MerCruiser Alpha One Gen 2 (Replaces...
Product Details
This Lower Gearcase Seal Kit is engineered for MerCruiser Alpha One Gen 2 sterndrives manufactured from 1991 to the present, specifically fitting serial numbers 0D469859 and up. It includes all the essential gaskets, seals, and O-rings required to service the lower unit, preventing water intrusion and gear lube leakage.
It serves as a direct cross-reference for MerCruiser part numbers 26-816575A3 and 26-816575A1, as well as popular aftermarket equivalents including Sierra 18-2646-1, GLM 87511, and Mallory 9-74206.
- Installation method: Direct replacement for original parts.
- Core function: Prevents leakage of gearcase lubricant.
- Build: Ensures reliable operation of the drive unit.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| MerCruiser | 26-816575A3 |
| MerCruiser | 26-816575A1 |
| Sierra | 18-2646-1 |
| GLM | 87511 |
| Mallory | 9-74206 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser compatibility, ensure your sterndrive is an Alpha One Gen 2 model (1991 and newer) with a serial number of 0D469859 or later.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen 2 Sterndrives | Various | 4-Stroke | 1991–present | 26-816575A3, 26-816575A1 | Fits serial # 0D469859 and later |
Technical Specs
- Product Type
- Lower Gearcase Seal Kit
- Installation
- Direct replacement
- Dimensions
- As per OEM specifications
- Warranty
- Varies by manufacturer (typically 1 year)
- Other Technical Attributes
- Prevents leakage of the gearcase; ensures normal operation of drive unit
What’s in the Box
- 1 x Carrier Seal (821759A2)
- 1 x Impeller Gasket (27-43033-1)
- 1 x Seal Ring (26-45577)
- 1 x Impeller Gasket (27-817277)
- 1 x Oil Seal (26-8164641)
- 1 x Oil Seal (26-12224)
- 1 x Face Seal (8M2014338)
- 2 x Drain Screw Gasket (26-830749)
- Various O-Rings
Installation Notes
A typical installation involves the following steps. Always consult a service manual specific to your drive model for detailed instructions and torque specifications.
- Drain the gear lube from the lower unit completely.
- Remove the propeller assembly.
- Unbolt and carefully detach the lower unit from the upper housing.
- Disassemble the gearcase as needed to access the carrier and shaft seals.
- Carefully remove all old seals, gaskets, and O-rings, taking care not to scratch any sealing surfaces.
- Thoroughly clean all components and mating surfaces of old sealant and debris.
- Lightly lubricate new seals and O-rings with 2-4-C grease or gear oil before installation.
- Install the new components from the kit using appropriate seal drivers to ensure they are seated correctly.
- Reassemble the lower unit, applying sealant to bolts as specified by the manufacturer.
- Pressure and vacuum test the gearcase to confirm seal integrity before refilling with lube.
- Refill the gearcase with high-quality marine gear lubricant to the proper level.
- Reinstall the propeller and conduct a final inspection.
Troubleshooting & FAQ
How do I confirm this kit fits my sterndrive?
This kit is specifically designed for MerCruiser Alpha One Generation 2 sterndrives made from 1991 to the present. The most important check is your drive's serial number, which must be 0D469859 or later. This kit will not fit Alpha One Gen 1 models or any other sterndrive series.
What are the common signs of a failing gearcase seal?
The most common symptoms are milky, water-contaminated gear lube (check by loosening the bottom drain screw), visible oil leaks around the propeller shaft or drain plugs, or a frequent need to top off the gear lube. You may also notice a distinct burning oil smell after running the engine.
How often should these seals be replaced?
It's best practice to replace lower unit seals preventatively every 2-3 years, especially in saltwater environments. They should always be replaced whenever the lower unit is serviced for other reasons (like a water pump replacement) or immediately if a leak is detected.
Do I need special tools for this job?
Yes, professional installation is recommended because specialized tools are required. These typically include a bearing carrier retainer wrench to remove the prop shaft bearing carrier, a proper seal driver set to install seals without damage, and a pressure/vacuum tester to verify the repair was successful.
Is this an OEM MerCruiser part?
This is an aftermarket replacement part, not an original equipment manufacturer (OEM) component. It is engineered to meet or exceed OEM specifications for fit, form, and function, providing a reliable and cost-effective alternative.
What is your shipping policy?
We ship worldwide quickly, with typical transit times of 5–15 days for most regions. Standard shipping is free on all orders. Expedited shipping options, if available for your location, will be presented at checkout.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard policy window for items that are unused and in original condition. Please see our full policy page or contact us for instructions.
Safety & Important Info
- Verify images/specifications vs 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.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
