Martyr CMM30 Zinc Hull Anode | 6” x 2.67” x 0.56” | Bolt-On | Saltwater

Martyr Zinc Hull Anode — CMM30 | Saltwater

A bolt-on zinc hull anode for saltwater use. The CMM30 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 6-inch length and low-profile height make it well suited for hull areas where a longer but shallower anode footprint is needed.

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: CMM30
• Brand: Martyr Anodes
• Anode Material: Zinc
• Anode Type: Bolt-On Hull Anode
• Best Use: Saltwater environments

Dimensions

• Length: 6” (152.4 mm)
• Width: 2.67” (67.8 mm)
• Height: 0.56” (14.2 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
• Hull areas requiring a longer, lower-profile anode footprint
• Saltwater operating environments

CMM Series — Comparing Sizes

• CMM24 — smaller bolt-on zinc hull anode (4.36” x 1.92” x 0.7”)
• CMM30 (this part) — mid-size bolt-on zinc hull anode (6” x 2.67” x 0.56”)
• CMM25 — larger bolt-on zinc hull anode (9.08” x 3.25” x 0.72”)

Related Hull Anodes

• Martyr CMDIVERZ Zinc Hull Plate Anode – ½” x 6” x 12” — larger zinc hull plate anode
• Martyr CMDIVERHZ Heavy Zinc Hull Plate Anode – 1” x 6” x 12” — heavy-duty zinc hull plate
• Martyr CMDIVERMINI Zinc Mini Hull Plate Anode – 6” x 4” x ½” — compact 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 CMM30 is a good choice when you need a longer anode footprint than the CMM24 provides but don’t need the full width of the CMM25 — its lower profile height also makes it suitable for hull areas with limited clearance above the waterline. 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.