Sierra 18-2599

Upgrading or repairing your Mercury Marine outboard just got simpler with the Sierra 18-2599 seal and tool kit. Designed as a direct replacement for OEM part number 26-816575A 2, this kit tackles one of the most common pain points for boaters: crankshaft seal failures that lead to oil leaks, reduced performance, and costly downtime on the water.

Why Crankshaft Seals Fail and When to Replace Them

Crankshaft seals endure extreme conditions—high RPMs, heat from combustion, and constant exposure to saltwater or fuel residues. Over time, they harden, crack, or lose their seal, allowing oil to seep into the crankcase or exhaust. You'll notice symptoms like blue smoke from the exhaust, low oil levels without visible external leaks, or a burning oil smell. Replacing them proactively during routine maintenance can prevent engine seizure and extend the life of your powerhead.

The Sierra 18-2599 kit isn't just a seal—it's a complete solution with precision tools for flawless installation, ensuring you get a like-new seal without the guesswork.

Key Features of the Sierra 18-2599 Kit

• High-Quality Materials: Viton or equivalent elastomers resist heat up to 400°F and chemicals better than standard rubber, outlasting generics.
• Exact OEM Dimensions: Matches Mercury's specs for 1.5-inch crankshafts, preventing alignment issues.
• Specialized Installation Tools: Includes a driver and seal protector to avoid damaging the new seal during install— a common DIY mishap.
• Corrosion-Resistant Construction: Tools feature zinc plating for marine environments.
• Kit Completeness: Everything in one package, no hunting for extras.

Compatibility with Mercury Marine Engines

This kit fits a wide range of Mercury outboards, particularly inline 4-cylinder and V6 models from the 1980s through early 2000s. Common applications include:

• 115-140 HP 4-cylinders (serial numbers starting with 0D, 0E, 0G)
• 175-225 HP V6 models (serial 0F, 0M, 1B)
• Pro Max and Sport Jet variants with matching crank dimensions

Always cross-reference your engine's serial number plate for the best fit. Sierra's engineering ensures drop-in replacement without modifications.

Step-by-Step Installation Guide for DIY Boaters

With basic tools and mechanical know-how, you can swap this in a weekend. Here's a proven process:

1. Prep Work: Drain oil, remove powerhead from midsection, and secure flywheel with a holding tool.
2. Seal Removal: Use a seal puller or screwdriver to extract the old seal carefully, avoiding crankshaft damage.
3. Clean and Inspect: Wipe the crank journal spotless and check for scoring—hone lightly if needed.
4. Install New Seal: Lubricate with assembly lube, use the protector sleeve, and tap evenly with the driver tool until flush.
5. Reassemble: Torque to spec (around 15-20 ft-lbs for flywheel nut), refill oil, and test run.

Pro Tip: Chill the seal in the freezer for 30 minutes beforehand—it contracts slightly for easier insertion.

Benefits of Choosing Sierra Over OEM Parts

Sierra delivers factory-level quality at a fraction of Mercury prices, backed by decades of marine aftermarket expertise. Boaters rave about the durability—many report zero leaks after 300+ hours. It's not just cheaper; it's smarter for frequent haulers or charter ops where downtime kills profits. Plus, Sierra's U.S.-based support means quick answers if questions arise.

Maintenance Tips to Maximize Seal Life

To keep your new Sierra seal thriving:

• Change oil every 100 hours with marine-grade synthetic.
• Flush cooling system post-saltwater use.
• Monitor for prop strike damage, which stresses seals.
• Winterize properly to avoid condensation buildup.

Pair with regular compression tests to catch issues early.