Martyr CM875821Z Zinc Duo Prop Ring Anode – Volvo Penta DuoProp | Saltwater
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Martyr Zinc Duo Prop Ring Anode — Volvo Penta DuoProp | Part No. CM875821Z
Replace the ring anode on your Volvo Penta DuoProp (counter-rotating dual propeller) sterndrive with this zinc-alloy unit from Martyr Anodes. The ring anode fits around the propeller hub assembly on the DuoProp drive and provides sacrificial protection for the propeller hub, shaft, and surrounding hardware against galvanic corrosion in saltwater environments.
Zinc is the traditional choice for saltwater use. However, for Volvo Penta DuoProp drives with aluminum hub components, the aluminum CM875821A is generally the preferred alloy — it provides equivalent protection while being less likely to cause galvanic issues with aluminum hardware. If you operate in freshwater, see the magnesium alternative linked below.
Part Information
- Part Number: CM875821Z
- Brand: Martyr Anodes
- Anode Material: Zinc
- Anode Type: Duo Prop Ring Anode
- OEM Reference: 875821
- Best Use: Saltwater environments
Compatible Applications
- Volvo Penta DuoProp Sterndrive — propeller hub ring anode position
- Saltwater operating environments
- Confirm OEM reference 875821 against your drive’s parts diagram before ordering
Choosing the Right Alloy
- Zinc (this part) — Saltwater use
- Aluminum — CM875821A — Saltwater and brackish water; preferred alloy for Volvo Penta aluminum drive components
- Magnesium — CM875821M — Freshwater use only
Related Products
- Martyr CMT-290DPKITA Aluminum Anode Kit – Volvo Penta 290 Dual Prop — complete DuoProp anode kit
- Volvo Penta DuoProp Front Propeller Nut 852196 — DuoProp front propeller hardware
- Volvo Penta DuoProp Rear Propeller Nut 21631162 — DuoProp rear propeller hardware
- Volvo Penta DuoProp Propeller Mounting Kit 854667 — DuoProp propeller mounting hardware
Service Interval
Inspect DuoProp ring anodes at every haulout and replace when worn to approximately 50% of original size. The propeller hub area is a high-exposure position — in high-galvanic marina environments, inspect more frequently as depletion can be faster than expected.
Parts Desk Insights
The DuoProp ring anode sits within the propeller hub assembly and is easy to overlook during routine anode checks — but it’s one of the most important anodes on the drive. The counter-rotating hub assembly involves dissimilar metals in close proximity, making it particularly vulnerable to galvanic corrosion if the anode is depleted. While zinc is a reliable saltwater anode material, the aluminum CM875821A is generally the preferred choice for Volvo Penta DuoProp drives: it provides equivalent protection in saltwater while being less likely to cause galvanic issues with the aluminum hub components. For a full DuoProp anode service, the CMT-290DPKITA complete anode kit covers all positions in one purchase and is the most efficient approach.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.