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)

This comprehensive seal kit is designed for MerCruiser sterndrives manufactured from 1983 to 2009. It fits a wide range of models, including R, MR, Alpha One, Alpha One Gen II, Bravo One, Bravo Two, and Bravo Three drives.

This kit is a direct replacement for Mercury part number 25-87400A2, Sierra 18-2649, and GLM 87400.

• Contains all necessary O-rings and seals to rebuild one trim cylinder.
• Features upgraded aftermarket seals made from high-grade Viton and urethane for superior durability and longevity compared to standard OEM materials.
• Engineered to meet or exceed OEM specifications for a reliable, leak-free seal.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This kit includes all the necessary O-rings and seals for a complete rebuild of one trim cylinder.

Explosion Diagram

Installation Guide

1. Safely secure the sterndrive in the fully raised position before beginning work.
2. Disconnect the hydraulic lines from the trim cylinder, preparing for fluid spillage.
3. Remove the hinge pins or bolts securing the cylinder to the transom and drive.
4. Carefully remove the cylinder from the boat.
5. Disassemble the cylinder end cap and piston assembly, noting the orientation of all seals.
6. Remove the old O-rings and seals from the grooves, exercising caution not to scratch the metal surfaces.
7. Thoroughly clean all components with a suitable solvent and inspect for any damage or wear.
8. Lubricate the new seals with hydraulic fluid or assembly lube before installation.
9. Carefully install the new seals, ensuring they are properly seated and not twisted.
10. Reassemble the cylinder and torque all fasteners to the manufacturer's specifications.
11. Reinstall the cylinder on the boat, reconnect hydraulic lines, and bleed the system to remove all air.
12. Test the trim/tilt system for smooth operation and check for any leaks.

Troubleshooting & FAQ

How can I be sure this kit fits my MerCruiser drive?
This kit is compatible with MerCruiser R, MR, Alpha One, Alpha One Gen II, and Bravo series drives manufactured between 1983 and 2009. Please check the 'Compatible Engine Models' table to confirm your specific model and year. Verifying the OEM part number 25-87400A2 is the best way to ensure a match.

What's the difference between this kit and the original Mercury part?
Our aftermarket kit uses premium Viton and high-grade urethane seals, which offer superior resistance to chemicals, heat, and abrasion compared to the standard nitrile materials used in the OEM kit. This provides enhanced durability and a longer service life.

Is this kit for one or both trim cylinders?
This kit contains all the seals required to rebuild one trim cylinder. If you need to service both cylinders on your sterndrive, you will need to purchase two kits.

What are the signs that my trim cylinder seals are failing?
Common symptoms include hydraulic fluid leaking from the cylinder end caps, a spongy or delayed response from the trim/tilt system, or the drive failing to hold its position and 'drifting' down over time.

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.