Trim Cylinder O-Ring Rebuild Kit - Fits MerCruiser R, MR, Alpha One, Alpha One Gen II & Bravo Drives (25-87400A2)
Trim Cylinder O-Ring Rebuild Kit - Fits MerCruiser R, MR, Alpha One, Alpha One Gen II & Bravo Drives (25-87400A2) 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
Trim Cylinder O-Ring Rebuild Kit - Fits MerCruiser R, MR, Alpha One...
Product Details
This Trim Cylinder O-Ring Rebuild Kit is designed to service worn or leaking trim cylinder seals on MerCruiser stern drives. It is compatible with a wide range of models manufactured from 1983 to 2009, including R, MR, Alpha One, Alpha One Gen II, Bravo One, Bravo Two, and Bravo Three series.
This kit serves as a direct replacement for Mercury part number 25-87400A2, Sierra 18-2649, and GLM 87400.
- Installation is required during a full trim cylinder rebuild.
- This aftermarket kit features seals made from high-grade Viton and urethane for enhanced durability and chemical resistance compared to standard OEM materials.
- Each kit contains all necessary O-rings and seals to rebuild one trim cylinder.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury | 25-87400A2 |
| Sierra | 18-2649 |
| GLM | 87400 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure accurate fitment.
This kit fits a wide variety of MerCruiser sterndrive and transom assemblies produced between 1983 and 2009.
| Brand | Model | Years | OEM Part No. |
|---|---|---|---|
| MerCruiser | R/MR/ALPHA ONE (Sterndrive) | 1983–1990 | 25-87400A2 |
| MerCruiser | R/MR/ALPHA ONE (Transom Assembly) | 1983–1990 | 25-87400A2 |
| MerCruiser | ALPHA ONE (GEN.II) | 1991–1995 | 25-87400A2 |
| MerCruiser | ALPHA ONE (GEN.II) | 1996–1997 | 25-87400A2 |
| MerCruiser | ALPHA ONE (GEN.II) | 1998–2009 | 25-87400A2 |
| MerCruiser | BRAVO ONE | 25-87400A2 | |
| MerCruiser | BRAVO TWO | 25-87400A2 | |
| MerCruiser | BRAVO THREE | 25-87400A2 | |
| MerCruiser | BRAVO X ONE | 25-87400A2 | |
| MerCruiser | BRAVO X TWO | 25-87400A2 | |
| MerCruiser | BRAVO X THREE | 25-87400A2 | |
| MerCruiser | BRAVO XR ONE | 25-87400A2 | |
| MerCruiser | BRAVO XR SPORTMASTER | 25-87400A2 | |
| MerCruiser | BRAVO XR THREE | 25-87400A2 | |
| MerCruiser | BRAVO XZ ONE | 25-87400A2 | |
| MerCruiser | BLACKHAWK | 1994–1995 | 25-87400A2 |
| MerCruiser | HI PERFORMANCE TRANSOM | 25-87400A2 | |
| MerCruiser | INTEGRATED TRANSOM | 25-87400A2 |
Technical Specs
- Product Type
- Trim Cylinder Seal Kit
- Installation
- Required during cylinder rebuild
- Weight
- 0.05 lbs (0.02 kg)
- Warranty
- Five Star Marine: 2 Year Warranty
- Materials
- Aftermarket kit uses Viton and high-grade urethane seals for superior durability.
What’s in the Box
- O-rings and seals sufficient for rebuilding one (1) MerCruiser trim cylinder.
Installation Notes
- Disconnect the vessel's battery to prevent accidental operation of the trim system.
- Support the sterndrive securely with a blocking stand to prevent it from falling.
- Remove the hydraulic lines and cap the ends to prevent fluid loss and contamination.
- Remove the upper and lower pins securing the trim cylinder to the transom and drive.
- Carefully remove the cylinder from the vessel.
- Using a spanner wrench, unscrew the end cap of the cylinder body.
- Slide the piston rod assembly out and carefully remove all old O-rings and seals, noting their orientation.
- Thoroughly clean all components, ensuring no debris remains in the seal grooves.
- Lubricate the new seals with hydraulic fluid and install them in their respective grooves.
- Reassemble the cylinder, tighten the end cap to the manufacturer's torque specification.
- Reinstall the cylinder on the vessel, reconnect hydraulic lines, and bleed the system according to your service manual.
- Test for smooth operation and check for any leaks.
Troubleshooting & FAQ
How do I know if my trim cylinders need rebuilding?
Common signs include visible hydraulic fluid leaks around the cylinder end caps or rods, a "spongy" or weak trim response, or if the sterndrive slowly drifts down from its trimmed position over time.
How many cylinders does one kit service?
This kit contains all the necessary seals to rebuild one individual trim cylinder. Most MerCruiser sterndrive setups use two cylinders, which would require purchasing two kits for a complete overhaul.
What is the main difference between this kit and the OEM version?
Our aftermarket kit is designed to meet or exceed OEM specifications. The primary difference is the use of upgraded materials—specifically Viton and high-grade urethane—which offer superior resistance to chemicals, heat, and abrasion compared to the standard nitrile rubber used in many OEM kits.
Will this kit fit my specific sterndrive model?
This kit fits a very broad range of MerCruiser drives from 1983-2009, including Alpha and Bravo series. Please review the 'Engine & Model Compatibility' table and cross-reference your OEM part number to ensure a perfect match.
What common tools are required for this job?
You will typically need a set of marine-grade wrenches, a spanner wrench to open the cylinder cap, picks or small screwdrivers to remove old seals, a torque wrench, clean rags, and the correct type of hydraulic trim fluid.
Is bleeding the hydraulic system necessary after installation?
Yes, any time the hydraulic system is opened, air can enter. Bleeding the system is critical to remove trapped air, ensure smooth and responsive trim operation, and prevent damage to the hydraulic pump.
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 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.
