Trim Cylinder O-Ring Kit – Fits MerCruiser R, MR, Alpha One, Gen II & Bravo (Replaces 25-87400A2)

$35.99 $57.00

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Trim Cylinder O-Ring Kit – Fits MerCruiser R, MR, Alpha One, Gen II & Bravo (Replaces 25-87400A2) is backordered and will ship as soon as it is back in stock.

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

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This Trim Cylinder O-Ring Kit – Fits MerCruiser R, MR, Alpha One, Gen II & Bravo (Replaces 25-87400A2) contains all the necessary seals to rebuild a single power trim cylinder on various MerCruiser sterndrives, including R, MR, Alpha One (Gen I & II), and Bravo models manufactured between 1983 and 2015. It is engineered for a precise fit to restore hydraulic integrity and prevent leaks.

It serves as a direct replacement for Mercury/MerCruiser part number 25-87400A2, Quicksilver 87400A2, and Sierra 18-2649, ensuring broad compatibility for maintenance and repairs.

Engineered for direct replacement installation.
Includes an 11-piece O-ring set for rebuilding one cylinder.
Constructed from high-quality rubber/elastomer materials for durability.

Part Number Matrix

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

Brand	Part Number
Mercury/MerCruiser	25-87400A2
Quicksilver	87400A2
Sierra	18-2649

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This kit is designed for a wide range of MerCruiser sterndrives. Please verify your drive's model and serial number against the compatibility list to ensure a correct fit.

Brand	Model	Rated HP	Years	OEM Part No.	Notes
MerCruiser	R/MR/Alpha One	All	1983–1990	25-87400A2	For serial numbers 6225577-0D469858
MerCruiser	Alpha One SS	All	1986–1989	25-87400A2	For serial numbers 0A545004 and up
MerCruiser	Alpha One Gen II	All	1991–2015	25-87400A2	For serial numbers 0D469859-2A480243
MerCruiser	Bravo	All	1988–2015	25-87400A2	For serial numbers 0B664190-2A480243
MerCruiser	Bravo SeaCore	All	2007–2015	25-87400A2	For serial numbers 0W900000-2A480243
MerCruiser	Blackhawk	All	1994–1995	25-87400A2	For serial numbers 0F186717 and up

Technical Specs

Product Type: Trim Cylinder O-Ring/Seal Kit
Installation: Direct replacement
Housing Material: Rubber/elastomer (O-rings)
Housing Color: Black
Weight: 0.05 lb (0.023 kg)
Other Technical Attributes: 11-piece O-ring replacement kit

What’s in the Box

11 x O-rings (25-87400A2)

Installation Notes

Safely secure the vessel on a trailer or lift and lower the sterndrive to the full down position.
Place a suitable container under the work area to catch any hydraulic fluid spillage.
Disconnect the hydraulic lines from the trim cylinder, carefully noting their orientation.
Remove the mounting hardware and detach the cylinder from the sterndrive.
Carefully disassemble the cylinder end cap using appropriate tools to access the internal seals.
Remove the old O-rings, taking care not to scratch the sealing surfaces or grooves.
Thoroughly clean the cylinder body and piston rod, ensuring all seal grooves are free of debris.
Lightly lubricate the new O-rings with fresh power trim fluid before carefully seating them in their grooves.
Reassemble the cylinder, ensuring all components are correctly aligned and torqued to manufacturer specifications.
Reinstall the cylinder onto the sterndrive and reconnect the hydraulic lines.
Top off the power trim fluid reservoir and bleed the system by cycling the drive up and down several times.
Inspect for any leaks and verify smooth, correct operation of the trim system.

Troubleshooting & FAQ

How do I know if this o-ring kit fits my specific MerCruiser drive?

Confirm your fitment by checking the 'Engine & Model Compatibility' table. It is critical to match your drive model, year, and especially the serial number range listed to ensure this kit is correct for your application.

Will this kit fix a hydraulic fluid leak?

Yes, this kit is intended to resolve external hydraulic fluid leaks by replacing the aged or failed O-rings on the trim cylinder body. Failed seals are the most common cause of such leaks.

What are the signs of a failing trim cylinder seal?

Common symptoms include visible hydraulic fluid weeping from the cylinder end caps, a slow "drift down" of the sterndrive when trimmed up, or a sluggish and ineffective trim system response.

How often should I replace my trim cylinder O-rings?

There is no manufacturer-defined replacement interval. It's best to replace them whenever you notice a leak, experience performance issues, or as preventative maintenance during a major sterndrive service.

Is any special lubricant required for installation?

Yes, always lubricate new O-rings with a small amount of clean, fresh power trim hydraulic fluid or a dedicated O-ring assembly lubricant. This prevents the seals from tearing or getting pinched during installation.

Does this kit contain every seal inside the cylinder?

This kit contains the 11 essential O-rings for rebuilding one cylinder's primary sealing points. Please review the 'What’s in the Box' section and product images to ensure it meets the needs of your specific repair.

What is the difference between OEM and aftermarket parts?

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.

What are your shipping speed and cost?

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

What is the warranty and return policy?

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.

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