Keep your Mercury running like new with this genuine **GEAR HOUSING ASSEMBLY, Basic**. Built to the same exacting standards as your original equipment for worry-free boating.

Factory-built to exact Mercury Marine specifications, this gear assembly ensures reliable operation across all engine RPM ranges. Part number 859399T18 is manufactured to exact Mercury Marine factory specifications for precision installation and optimal performance. Constructed from premium marine-grade materials designed to withstand harsh saltwater and freshwater environments.

Factory parts exist for a reason – they work. Part 859399T18 undergoes rigorous Mercury Marine quality testing that aftermarket manufacturers skip. The result? Reliable performance season after season.

FITS: 200-225HP MARINER, MERCURY

• Fits MARINER, MERCURY 200-225HP engines
• Compatible HP: 200HP, 225HP
• Covers 24 serial number ranges
• Configurations: Outboard
• OEM genuine Mercury Marine part

COMPLETE SERIAL NUMBER COMPATIBILITY:

200HP Models

• 200HP OUTBOARD (Mariner): 0T750164-0T800999, 0T801000-1B417701, 0G960500-0T178499, 0T178500-0T598999, 0T599000-0T800999, 0T801000-1B417701, 1B417702-1B504988
• 200HP OUTBOARD (Mercury): 0T980000-1B417701, 1B417702-1B504988, 0T750164-0T800999, 0T801000-1B417701, 1B417702-1B504988, 0G960500-0T178499, 0T178500-0T598999, 0T599000-0T800999, 0T801000-1B417701, 1B417702-1B504988

225HP Models

• 225HP OUTBOARD (Mariner): 0G760300-0T408999, 0G760300-0T408999, 0T409000-0T800999, 0T801000-1B417701
• 225HP OUTBOARD (Mercury): 0G760300-0T408999, 0G760300-0T408999, 0T409000-0T800999

Don’t know where your serial number is? Our quick reference guide shows exactly where to find it on Mercury engines.

Verify part 859399T18 works with your Mercury using our parts finder tool. Have questions? Reach out using the contact buttons at the bottom of this page – our team is here to help by text, call, or email.

Trusted Mercury Marine parts specialist since 1985. Save up to 20% below retail on factory Mercury Marine parts.