Martyr CMC03 Zinc Limited Clearance Shaft Anode – Stainless Allen Screw | Saltwater

Martyr Zinc Limited Clearance Shaft Anode — CMC03 | Saltwater

A zinc sacrificial shaft anode designed for propeller shaft installations where a standard round anode won’t fit due to tight clearances near the hull, strut, or cutlass bearing. The CMC03 is the largest unit in the CMC limited clearance series, suited to the biggest shaft diameters in this range. Secured with a stainless steel Allen head screw for a clean, tool-accessible installation.

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

Part Information

• Part Number: CMC03
• Brand: Martyr Anodes
• Anode Material: Zinc
• Anode Type: Limited Clearance Shaft Anode
• Fastener: Stainless steel Allen head screw
• Best Use: Saltwater environments with tight shaft clearances; largest CMC series shaft diameter

Compatible Applications

• Propeller shafts with limited clearance to hull, strut, or cutlass bearing
• Inboard and shaft-drive installations where standard round shaft anodes will not fit
• Largest shaft diameter in the CMC limited clearance series — confirm shaft diameter compatibility before ordering
• Saltwater operating environments

CMC Series — Choosing the Right Size

• CMC01 — smallest limited clearance shaft anode (lightest / smallest shaft diameter)
• CMC02 — mid-size limited clearance shaft anode (medium shaft diameter)
• CMC03 (this part) — largest limited clearance shaft anode (largest shaft diameter in this series)

Related Shaft Anodes

• Aluminum Streamline Shaft Anode 1” — CMT-X03AL — streamline profile for reduced drag
• Zinc Streamline Shaft Anode 1-1/2” — CMT-X07 — streamline zinc shaft anode
• Zinc Shaft Anode 4” — CMT-X17 — larger zinc shaft anode
• Zinc Shaft Anode MDX-5 1-1/4” — standard profile zinc shaft anode
• Zinc Shaft Anode MDX-7 1-1/2” — standard profile zinc shaft anode

Service Interval

Inspect shaft anodes at every haulout and replace when worn to approximately 50% of original size. Shaft anodes can deplete faster than hull or drive anodes due to their direct exposure on the rotating shaft — inspect more frequently on vessels kept in high-galvanic marina environments.

Parts Desk Insights

The CMC03 is the largest of the three CMC limited clearance shaft anodes — if you’re unsure which size fits your shaft, the key measurement is the shaft diameter and the available clearance between the shaft and the nearest fixed structure (strut, hull, or cutlass bearing housing). If you have the space for a standard round profile, a full-round anode provides more sacrificial mass and longer service life between replacements. The stainless Allen screw makes installation and removal straightforward, but always confirm the anode has solid metal-to-metal contact with the shaft — a loose fit or painted shaft surface will prevent the anode from working. Compare shaft diameter against all three CMC part specifications before ordering to ensure the correct fit.