Alpha 1 & Gen. 2 Outdrive Parts *Drawings *Videos

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Mercruiser Alpha One plug (upper gearcase)

Mercruiser outdrive upper gear case plug

  • GLM P/N 21890 plastic plug replaces OEM 19-47579, Sierra 18-3232
  • Installs into the upper gear housing
  • Compatible with models up to 1990 (does not work with Generation 2)

Tech support exploded view Alpha One drawings
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21890 Plug

21890 Plug

P/N 21890 Plug $4.29

Customers who ordered P/N 80190 also purchased:

26-32511A1 Seal Kit Parts 87500
26-32511A1 Seal Kit Parts 87500

P/N 87500 Upper gear case seal and gasket kit for all models up to 1990. Replaces OEM 26-32511A1. $24.15

P/N 87501 Upper seal kit for Alpha 1 Generation 2 (1991 and up) models. Replaces OEM 26-32511A1. $20.15

317201 Large Sealant-Johnson
317201 Large Sealant-Johnson

P/N 317201 Gasket sealant (includes brush inside lid). $24.15