Sierra 18-99525 Lower Unit Gear Oil Filler Adapter Kit

The Sierra 18-99525 is a lower unit gearcase lubrication oil filler adapter kit designed for broad compatibility across the most popular marine outboard and inboard-outboard (I/O) engine brands. Whether you're performing routine gear oil maintenance or a full lower unit service, this kit provides the correct threaded and unthreaded adapters to connect your gear lube pump or fill tube to virtually any gearcase.

Compatible Brands Include:

• Mercury & Mariner
• MerCruiser
• Johnson & Evinrude
• Yamaha
• Suzuki
• Tohatsu
• Volvo Penta
• Chrysler & Force

Kit Includes (5 Adapter Components):

• Metric M8 x 1.25P thread adapter (551-334M)
• Suzuki-specific M10 x 1.25P thread adapter (551-334S)
• Volvo Penta M10 x 1.5P thread adapter (551-334V)
• 3/8 x 16P threaded nozzle adapter (551-33TN)
• Unthreaded nozzle adapter (551-33UN)

Sierra is a trusted name in the marine aftermarket industry, producing high-quality replacement and maintenance parts for outboard, inboard, and sterndrive applications. The 18-99525 adapter kit eliminates the guesswork during lower unit oil changes by providing all the fittings needed for multi-brand service in a single, convenient package.