Martyr CM852835M Magnesium Transom Bar Anode – Volvo Penta SX/DP | Freshwater
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Martyr Magnesium Transom Bar Anode — Volvo Penta SX/DP | Part No. CM852835M
Replace the transom bar anode on your Volvo Penta SX or DP sterndrive with this magnesium-alloy unit from Martyr Anodes. The transom bar anode mounts across the transom bracket assembly and provides sacrificial protection for the surrounding hardware against galvanic corrosion.
Magnesium is the correct alloy for freshwater environments, where zinc and aluminum anodes are too electrochemically passive to provide adequate protection. If you operate in saltwater or brackish water, see the aluminum alternative linked below.
Part Information
- Part Number: CM852835M
- Brand: Martyr Anodes
- Anode Material: Magnesium
- Anode Type: Transom Bar Anode
- OEM Reference: 852835
- Best Use: Freshwater environments
Compatible Applications
- Volvo Penta SX Sterndrive — transom bar position
- Volvo Penta DP Sterndrive — transom bar position
- Freshwater operating environments only
Choosing the Right Alloy
- Magnesium (this part) — Freshwater use only
- Aluminum — CM852835A — Saltwater and brackish water; also the preferred alloy for aluminum drive components
Related Products
- Volvo Penta SX Sterndrive Zinc Anode Kit – 3588770 — complete SX drive anode kit
- Volvo Penta SX Zinc Anode Kit VPSXKZ — alternate complete SX anode kit
Service Interval
Inspect transom bar anodes at every haulout and replace when worn to approximately 50% of original size. Magnesium anodes in freshwater deplete at a moderate rate — inspect annually and replace promptly to maintain continuous protection on the transom bracket hardware.
Parts Desk Insights
The transom bar is one of the most exposed anode positions on a Volvo Penta sterndrive and is often the first to show significant wear. Magnesium is the right alloy for freshwater use — the most common mistake we see is customers installing zinc anodes in freshwater lakes, where zinc doesn’t corrode fast enough to provide meaningful protection. If your boat operates in saltwater or moves between fresh and salt water, the aluminum CM852835A is the better choice: it protects reliably in both environments and is less likely to cause galvanic issues with the aluminum drive components than zinc. Don’t wait for this anode to fully deplete before replacing — once it’s gone, the transom bracket hardware starts corroding quickly.
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.