Mercury Quicksilver Lower Unit Seal Kit 26-33144A2 | MerCruiser IA IB IC R MR Alpha One Gen 1

Lower Gearcase Reseal Kit for Legacy MerCruiser Sterndrives

The Mercury Quicksilver 26-33144A2 is an OEM lower unit seal kit designed to fully reseal the lower gear housing on select vintage MerCruiser sterndrives. It includes the oil seals, O-rings, and gaskets needed to restore a watertight lower gearcase — keeping gear lubricant in and water out. This is the correct kit for a complete lower unit reseal rather than replacing individual seals one at a time.

Part Information

• Part Number: 26-33144A2
• Short Reference: 33144A2
• Brand: Mercury / Quicksilver
• Official Product Type: Lower Gear Housing Seal Kit
• Barcode / UPC: 745061079359
• Supersedes: 26-33144A1, 26-89238A1
• Aftermarket Cross-References: Sierra Marine 18-2652, GLM Marine 87510

Compatible Applications

• MerCruiser IA sterndrive (1963 and up, serial 164188 and up)
• MerCruiser IB sterndrive
• MerCruiser IC sterndrive
• MerCruiser EZ Shift sterndrive
• MerCruiser MC-I sterndrive
• MerCruiser R sterndrive
• MerCruiser MR sterndrive
• MerCruiser Alpha One Generation 1 sterndrive (through approximately 1990)

Serial Number Requirement: Verify fitment against the drive serial number and the lower gear housing parts diagram before ordering. This kit does not apply to Alpha One Generation 2 or Bravo series drives.

System & Diagram Position

This kit services the lower gear housing assembly — the section of the sterndrive below the pivot point that houses the driveshaft, prop shaft, forward/reverse gears, and bearing carrier. In the MerCruiser parts diagram, this kit covers the sealing components in the lower gearcase section, including the prop shaft seal area, driveshaft seal bore, and associated O-rings and gaskets throughout the housing.

Kit Contents

The 26-33144A2 kit includes the seals, O-rings, and gaskets required for a complete lower gearcase reseal, typically covering:

• Prop shaft oil seals (inner and outer)
• Driveshaft seal
• Bearing carrier O-rings
• Drain and fill screw gaskets
• Associated housing O-rings and gaskets per the lower unit diagram

Confirm exact contents against the Mercury parts diagram for your specific drive serial number range.

When to Use This Kit

• Lower gearcase failed a pressure or vacuum leak test
• Gear lube is milky, water-contaminated, or leaking externally
• Prop shaft or driveshaft seals are weeping or blown
• Full lower unit teardown or rebuild
• Preventive reseal during a major service interval

Service Interval

Mercury recommends inspecting gear lube condition and checking for water contamination at least annually or every 100 hours of operation. A full lower unit reseal is typically performed when leaks are confirmed, during major drive service, or any time the lower housing is fully disassembled.

Installation Notes

• Full disassembly of the lower gearcase is required — this is not a quick-access service
• Use proper seal drivers and removal tools to avoid damaging seal bores
• Inspect prop shaft, driveshaft, and bearing carrier surfaces for scoring or wear before installing new seals
• Replace drain and fill screw gaskets included in the kit
• Pressure and vacuum test the reassembled lower unit before reinstalling on the drive
• Refill with the correct Mercury gear lube to the specified capacity

Related Parts

• MerCruiser Gearcase Drain Screw Seal – 8M0187157
• Mercury MerCruiser Alpha One Gen II Bearing Carrier Assembly 14587A7
• Quicksilver Needle Roller Bearing 30956T
• Quicksilver Bearing Carrier Key 30281
• Mercury MerCruiser Water Pump to Gear Housing Gasket 27-85610
• Mercury Mariner Lower Unit Gear Housing Seal Kit 26-43035A4
• Mercury MerCruiser Fish Line Cutting Seal 26-12224

Technical FAQ

Q: Does this kit fit Alpha One Generation 2?
A: No. The 26-33144A2 is for Generation 1 and earlier legacy drives (IA through Alpha One Gen 1). Alpha One Gen 2 and Bravo drives use different seal kits.

Q: Can I replace just the prop shaft seals instead of using the full kit?
A: You can, but if the drive failed a pressure test or has water-contaminated gear lube, a full reseal kit is the better approach. Replacing one seal while leaving aged O-rings and gaskets in place often leads to repeat leaks.

Q: What gear lube should I use after resealing?
A: Mercury High Performance Gear Lube or Quicksilver Gear Lube is recommended for MerCruiser sterndrives. Confirm the correct viscosity and capacity for your specific drive model in the Mercury service manual.

Q: Do I need a pressure tester after reassembly?
A: Yes. Mercury requires a pressure and vacuum test of the lower unit after any reseal service to confirm integrity before returning the drive to service.

Parts Desk Insights

Best use case: This kit is the right call any time the lower unit is coming apart — whether you're chasing a confirmed leak, dealing with milky gear lube, or doing a full drive rebuild. Buying the complete kit upfront avoids the common situation of needing to order additional seals mid-job once the housing is open.

Common mistakes: The most frequent error is ordering this kit for an Alpha One Generation 2 or Bravo drive — it does not fit. Always confirm the drive generation from the serial number tag before ordering. A second common mistake is skipping the pressure test after reassembly; a seal that looks seated correctly can still leak under pressure, and catching it on the bench is far easier than diagnosing it on the water.