MG Duff CM821631Mercury MerCruiser Block Anode

MG Duff CM821631Z / CM821631A Mercury MerCruiser Block Anode – Zinc / Aluminium

The MG Duff CM821631Z and CM821631A are sacrificial block anodes designed for compatible Mercury F.BB and MerCruiser E.B. marine propulsion installations. They provide replaceable sacrificial corrosion protection for electrically connected metallic components exposed to the marine environment.

The series includes two material options: zinc (CM821631Z) and aluminium (CM821631A). Both products are supplied individually and are intended for installations requiring the corresponding block anode configuration.

When correctly installed with appropriate electrical continuity, the sacrificial anode material corrodes preferentially, helping reduce galvanic corrosion of the protected metallic components.

Technical Specifications

Available Variants

Mercury and MerCruiser Compatibility

The MG Duff CM821631 series is identified in the supplied product information for the following applications:

• Mercury F.BB
• MerCruiser E.B.

The available data does not identify specific engine models, production years, sterndrive generations or original equipment part numbers.

Before ordering, verify the existing anode configuration and compatibility with the appropriate Mercury or MerCruiser assembly. The application designations alone should not be used to assume compatibility with all Mercury or MerCruiser propulsion systems.

Block Anode Construction

The CM821631 series features a block-style sacrificial anode configuration for the corresponding marine installation.

The supplied technical information confirms the manufacturer part numbers, available materials and application references. Overall dimensions, weight, fixing-hole measurements and fastening specifications are not provided.

These details should be checked against the existing anode or the manufacturer's technical drawing before selecting a replacement.

Zinc and Aluminium Sacrificial Corrosion Protection

The MG Duff CM821631 series is available in two sacrificial anode materials:

• Zinc – CM821631Z: Commonly used for galvanic corrosion protection in saltwater marine environments.
• Aluminium – CM821631A: Used in suitable marine corrosion protection systems, including saltwater and certain brackish-water conditions.

When correctly installed with suitable electrical continuity to the metallic components requiring protection, the sacrificial material corrodes preferentially, helping reduce galvanic corrosion.

The appropriate material should be selected according to the vessel's operating water conditions and the equipment manufacturer's recommendations.

Inspection and Replacement

Inspect the block anode periodically during routine marine propulsion system maintenance. Replace it when the sacrificial material becomes significantly depleted, physically damaged or no longer securely attached.

Before fitting a replacement, confirm the original anode configuration, inspect the mounting surfaces and follow the applicable equipment manufacturer's installation instructions.

Part Numbers and Product Identification

• MG Duff Zinc: CM821631Z
• MG Duff Aluminium: CM821631A
• Zinc EAN: 0628309100544
• Aluminium EAN: 0628309115494
• Application: Mercury F.BB / MerCruiser E.B.

Scope of Supply

1 × MG Duff Mercury / MerCruiser Block Anode in the selected material:

• CM821631Z – Zinc; or
• CM821631A – Aluminium.