SeaSierra Upper Unit Seal Kit for Mercruiser Alpha One Gen II 88397A1 — OEM-fit O-rings, oil seals & gaskets

If your Mercruiser Alpha One Gen 2 stern drive is leaking or due for preventative maintenance, this SeaSierra upper unit seal kit gathers the exact O-rings, oil seals and gaskets needed to rebuild the upper gearcase area. The kit is supplied to match OEM part numbers and fits Alpha I Gen II models produced across the 1991–1996+ serial ranges. Each component is selected to replicate form and fit so you can replace worn seals without sourcing multiple parts individually.

Which models and years does this SeaSierra kit fit?

This kit is compatible with Mercruiser Alpha I Gen II applications. It covers serial ranges and later production blocks commonly serviced in the field, making it suitable for many Alpha One Gen 2 stern drives.

• Fits Mercruiser Alpha I Gen II 1991–1995 (serial 0D469859–0F679999)
• Also compatible with 1996 and newer units (serial 0F680000 and up)
• Direct replacement for OEM 26-88397A1 / 88397A1

What parts are included in the 88397A1 upper unit seal kit?

The SeaSierra kit contains all the small seals and gaskets typically replaced during upper unit service so you don’t miss hidden leaks. Components are packed to simplify a single maintenance job instead of multiple part orders.

• O-rings: 25-25439, 25-35027, 25-35984, 25-70937, 25-32546
• Oil seals: 26-32080, 26-37259 and upper seal 26-88397
• Drain screw gasket(s) 12-19183 / 12-20260 and seal ring gasket 26-45577

How does this kit compare with OEM and other aftermarket parts?

SeaSierra supplies parts that match OEM dimensions and mating surfaces but at aftermarket value. The kit replaces known OEM numbers and is also cross-referenced to Mallory, GLM and Sierra equivalents, allowing straightforward substitution during repairs.

• Replaces OEM 26-88397A1 / 88397A1
• Cross-references Mallory 9-74302, GLM 87501, Sierra 18-2644
• Produced and packaged by SeaSierra with decades of marine parts experience

What should I prepare before installing the upper unit seal kit?

Gather basic tools, a clean workspace and the service manual for torque and disassembly steps to ensure correct installation. Inspect mating surfaces, shafts and bearings—seals only stop leaks when installed on sound hardware.

• Service manual or factory torque specs for your Alpha One Gen II
• Appropriate seal drivers, clean rags and compatible gear lube
• Check shafts and bearing condition; replace if scored or worn

Who is this for: The SeaSierra 88397A1 Upper Unit Seal Kit is intended for boat owners, marine mechanics and DIY technicians maintaining Mercruiser Alpha One Gen 2 stern drives. If you’re performing upper gearcase service, stopping leaks, or doing scheduled preventive maintenance on 1991–1996+ Alpha I Gen II units, this kit supplies the matching seals and gaskets to complete the job in one order.