Sierra 18-2590 Borg-Warner Seal Kit

Revitalize Your Marine Transmission with Precision Engineering

Keeping your boat's drivetrain in top shape demands reliable components that stand up to saltwater, heat, and constant vibration. This service kit targets the heart of Borg-Warner Velvet Drive 71 and 72 series transmissions, where seals bear the brunt of wear over years of service. Designed for boat owners who prioritize performance and longevity, it delivers everything needed for a thorough rebuild, restoring fluid-tight integrity and smooth operation.

Seals in these transmissions degrade from exposure to marine fluids, temperature swings, and mechanical stress, leading to leaks that compromise hydraulic pressure. A fresh set eliminates drips, prevents contamination, and ensures clutches engage crisply—critical for confident handling on the water.

Key Components and What They Do

• Input and Output Shaft Seals: Guard against gear oil seepage at high-RPM entry and exit points, maintaining lubrication where it counts.
• Pump Seals: Sustain pressure in the hydraulic system for reliable shifting between forward, neutral, and reverse.
• Converter Housing Seals: Seal the torque converter interface, preventing efficiency-robbing losses.
• Comprehensive Gaskets: Cover case halves and covers for a leak-proof assembly post-disassembly.

Each part is crafted from durable, oil- and heat-resistant materials suited to the demanding marine environment, outperforming stock replacements in endurance tests.

Perfect Fit for Popular Velvet Drive Models

Engineered specifically for Borg-Warner Velvet Drive 71C, 71L, 72C, and 72L series, this kit matches OEM specifications down to the micron. It's a go-to for mechanics servicing classic inboards from brands like Chris-Craft, Bertram, and Hatteras, where these transmissions powered generations of seaworthy hulls. Verify your model's gear ratios and mounting footprint during inspection to confirm compatibility—most 71/72 units from the 1960s through the 1980s pair seamlessly.

Installation Insights from Seasoned Mechanics

DIY-savvy boaters appreciate the straightforward rebuild process, but success hinges on preparation. Start by draining fluids and removing the transmission from the boat if space allows. Use a seal puller for clean extraction, avoiding scratches that invite premature failure. Lubricate new seals with assembly lube before pressing them in evenly with a driver tool—never hammer directly.

Pro Tips:

• Inspect bearings and clutches while apart; replace if scored for a complete refresh.
• Flush the cooler lines to evict debris that could gum up the works.
• Torque bolts to factory specs (typically 20-30 ft-lbs) in a crisscross pattern.
• Refill with ATF or manufacturer-spec oil, then cycle through gears in neutral to prime the pump.

Expect 4-8 hours for a full job, depending on access. Post-install, monitor for leaks during sea trials at varying loads.

Extend Transmission Life Beyond the Horizon

Beyond fixing leaks, proactive seal replacement heads off bigger issues like slipping clutches or total failure, which can sideline you mid-voyage. Pair this kit with routine fluid changes every 100 hours or annually, and check dipstick levels before each outing. In harsh saltwater duty, these upgrades can add seasons of trouble-free shifting, saving thousands in overhauls.

Boat owners report noticeably quieter operation and firmer shifts after installation, proving the investment in quality seals pays dividends on every trip.