Martyr CMMZ404 Zinc Hull Anode | 8.8” x 3.375” | Bolt-On | Saltwater

Martyr Zinc Hull Anode — CMMZ404 | Saltwater

A bolt-on zinc hull anode for saltwater use. The CMMZ404 mounts flush to the hull using its pre-drilled bolt hole pattern and provides sacrificial galvanic protection for the surrounding hull structure, through-hulls, and underwater metal fittings. Its 8.8-inch length and 3.375-inch width make it a mid-to-large bolt-on hull anode suited for vessels requiring substantial hull anode coverage.

Zinc is the traditional choice for saltwater environments. If you operate in freshwater, a magnesium alloy hull anode is the correct choice for that water type.

Part Information

• Part Number: CMMZ404
• Brand: Martyr Anodes
• Anode Material: Zinc
• Anode Type: Bolt-On Hull Anode
• Best Use: Saltwater environments

Dimensions

• Length: 8.8” (223.5 mm)
• Width: 3.375” (85.7 mm)
• Note: Hole dimension refers to the distance between mounting holes — confirm bolt pattern against your hull fitting before ordering

Compatible Applications

• Steel, aluminum, and fiberglass hull installations — bolt-on hull anode position
• Vessels requiring mid-to-large hull anode coverage in saltwater
• Saltwater operating environments

Related Hull Anodes

• Martyr CMM24 Zinc Hull Anode – 4.36” x 1.92” — smaller bolt-on zinc hull anode
• Martyr CMM30 Zinc Hull Anode – 6” x 2.67” — mid-size bolt-on zinc hull anode
• Martyr CMM40 Zinc Hull Anode – 7.3” x 2.6” — low-profile bolt-on zinc hull anode
• Martyr CMM25 Zinc Hull Anode – 9.08” x 3.25” — similar-size bolt-on zinc hull anode
• Martyr CMDIVERZ Zinc Hull Plate Anode – ½” x 6” x 12” — larger zinc hull plate anode
• Martyr CMDIVERA Aluminum Hull Plate Anode – ½” x 6” x 12” — aluminum option for saltwater and brackish water
• Martyr CMDIVERM Magnesium Hull Plate Anode – ½” x 6” x 12” — magnesium option for freshwater

Service Interval

Inspect hull anodes at every haulout and replace when worn to approximately 50% of original size. In high-galvanic marina environments or areas with significant stray current, inspect more frequently as depletion rates can vary considerably.

Parts Desk Insights

The CMMZ404 is a good choice for vessels that need a longer, wider bolt-on hull anode than the CMM30 or CMM40 provide, but don’t require the full surface area of a diver-style plate anode. At 8.8” x 3.375” it sits close in size to the CMM25 — if both fit your hull fitting, compare bolt patterns before ordering to confirm which is the correct match. As with all hull anodes, the most critical installation detail is ensuring the anode base makes direct metal contact with the hull: any paint, coating, or sealant between the anode and the hull surface will electrically isolate it and render it ineffective. If your boat operates in freshwater, switch to a magnesium alloy anode — zinc won’t corrode fast enough in low-conductivity water to provide meaningful protection.