Mercury Alpha One Zinc Anode CMT-821631Z

The CMT-821631Z is a zinc gimbal/block anode designed for Mercury Alpha One sterndrives, protecting the gimbal housing, transom plate, and surrounding drive components from galvanic corrosion. It is a direct replacement for OEM Mercury/Quicksilver part 821631.

Manufactured from marine-grade zinc alloy, this anode is intended for saltwater applications, where it sacrifices itself to protect more valuable aluminum and steel components.

Key Features

• Direct replacement for Mercury 821631 / 821631Q1
• Marine-grade zinc (saltwater optimized)
• Block-style / gimbal housing anode
• Protects transom and sterndrive mounting components
• Cast to MIL-spec corrosion standards

Engine / Drive Compatibility

Designed for:

• Mercury / MerCruiser Alpha One sterndrives
• Compatible with:
  • Alpha One Gen I
  • Alpha One Gen II
  • Some Bravo applications (gimbal use)

Installed on:

• Gimbal housing / transom plate

Protects:

• Gimbal ring and housing
• Transom assembly
• Adjacent bonded metals

Serial Number Fitment Notice

Always confirm:

• OEM reference (821631)
• Drive generation (Gen I vs Gen II)
• Mounting hole spacing and casting shape

When This Part Needs Replacement

• Anode is 50% or more consumed
• Uneven wear or pitting
• Visible corrosion on gimbal housing
• Routine seasonal service

Installation Notes

• Install on clean, bare metal surface
• Ensure full contact with mounting surface
• Do not paint the anode
• Replace mounting hardware if corroded
• Inspect regularly in saltwater

Alternate / Superseded Part Numbers

• Mercury / Quicksilver: 821631 / 821631Q1 / 821631B1
• Camp Company: CMT-821631Z
• Martyr: CM821631Z
• Aluminum version: CMT-821631A
• Magnesium version available

Parts Desk Insight

This is one of the most important single anodes on an Alpha drive. If its gone, corrosion targets the gimbal housing first, which is a high-cost repairso its one you never want to let fully deplete.

Shipping

Shipping: Ships same or next day for fast Canada wide shipping.