MG Duff CM55989 Mercury MerCruiser Button Anode, Ø31 × 30 mm

MG Duff CM55989 Mercury MerCruiser Button Anode – Zinc / Aluminium / Magnesium, Ø31 × 30 mm

The MG Duff CM55989 series consists of round sacrificial button anodes designed for compatible Mercury and MerCruiser marine propulsion applications. These replacement anodes help protect electrically connected metallic components against galvanic corrosion.

Three material versions are available: zinc (CM55989Z), aluminium (CM55989A) and magnesium (CM55989M). Each version has the same stated round body dimensions, allowing customers to select the appropriate sacrificial material for their corrosion protection system.

The anode has a specified body diameter of 31 mm and length of 30 mm. The product data also identifies a separate 1/2-inch diameter specification, whose precise measurement location is not defined in the supplied information.

Technical Specifications

Available Variants

Mercury and MerCruiser Compatibility

The MG Duff CM55989 button anodes are listed for compatible marine propulsion equipment manufactured by:

• Mercury
• MerCruiser

Specific engine models, sterndrive generations, production years and OEM part numbers are not identified in the available product information.

Before ordering, confirm compatibility with the existing anode and the applicable Mercury or MerCruiser parts documentation.

Round Button Anode Dimensions

The CM55989 series features a round sacrificial anode body with the following stated dimensions:

• Product diameter: 31 mm.
• Product length: 30 mm.
• Additional diameter reference: 1/2 inch.
• Body shape: Round.

The 1/2-inch measurement is identified separately from the 31 mm product diameter in the supplied specifications. Its exact function and measurement position should be confirmed against the original component or MG Duff technical drawing.

The available information does not specify the thread type, fixing method or overall weight.

Zinc, Aluminium and Magnesium Corrosion Protection

The MG Duff CM55989 series is available in three sacrificial anode materials:

• Zinc – CM55989Z: Commonly used for galvanic corrosion protection in saltwater marine environments.
• Aluminium – CM55989A: Suitable for appropriate marine corrosion protection systems, including saltwater and certain brackish-water applications.
• Magnesium – CM55989M: Generally used in freshwater corrosion protection systems.

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

Select the material according to the vessel's operating water conditions and the equipment manufacturer's recommendations.

Inspection and Replacement

Inspect the button 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 installation, confirm the existing anode dimensions, mounting arrangement and required material. Ensure suitable electrical contact with the metallic component requiring corrosion protection.

Part Numbers and Product Identification

• MG Duff Zinc: CM55989Z
• MG Duff Aluminium: CM55989A
• MG Duff Magnesium: CM55989M
• Zinc EAN: 0628309100629
• Aluminium EAN: 0628309115401
• Magnesium EAN: 0628309100612

Scope of Supply

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

• CM55989Z – Zinc; or
• CM55989A – Aluminium; or
• CM55989M – Magnesium.