SeaSierra Mercruiser Alpha One Gen II Upper Unit Seal Kit 88397A1 — Complete seals & gaskets

SeaSierra 88397A1 Upper Unit Seal Kit is a complete replacement seal set engineered to restore watertight integrity in Mercruiser Alpha One Gen II upper units.

This upper unit seal kit from SeaSierra contains the assortment of oil seals, O-rings, gaskets, and drain screw gasket you need to service Mercruiser Alpha I Gen II stern drives (model years listed). The kit matches common OEM part numbers and is intended for routine maintenance or repair where worn seals are allowing fluid loss or water ingress.

Which Mercruiser models and years does this kit fit?

The SeaSierra 88397A1 kit is made for Mercruiser Alpha One Gen II stern drives across specified serial ranges and later models. It covers early 1991–1995 units within the given serial blocks and all 1996 and newer units beginning at the indicated serial number.

• Compatible with Mercruiser Alpha I Gen II 1991–1995 (0D469859 - 0F679999).
• Compatible with 1996 & Up (0F680000 & Up).
• Replaces OEM 26-88397A1 and equivalent aftermarket numbers.

What parts are included in this upper unit seal kit?

The kit contains multiple seals and gaskets to service the upper unit without sourcing individual parts. SeaSierra bundles the exact sizes typically replaced during an upper unit overhaul so you can complete the job faster.

• Oil seals: 26-32080 and 26-37259 for shaft sealing.
• Seals and O-rings: 26-88397, 25-25439, 25-35027, 25-35984, 25-70937, 25-32546.
• Gaskets: drain screw gasket 12-19183 (12-20260) and seal ring gasket 26-45577.

How does this kit compare to OEM and other aftermarket options?

SeaSierra lists cross-reference numbers to mirror OEM fit and function while offering aftermarket value. The kit replaces known original part numbers and is supplied by a manufacturer experienced in marine engine parts since 1987.

• Direct replacement for OEM 26-88397A1 and compatible with Mallory, GLM, Sierra equivalents.
• Designed for straightforward installation using the same sealing points as the original parts.
• Quality control informed by decades servicing outboard and stern drive components.

Who is this for: This SeaSierra upper unit seal kit is aimed at boat owners, marine mechanics, and DIY enthusiasts working on Mercruiser Alpha One Gen II stern drives who need a full set of upper-unit seals and gaskets for service or repair. If you are replacing leaking seals, preparing a drive for winter storage, or performing preventative maintenance, this kit provides the matched components to get the upper unit reassembled correctly.