Sierra 18-6015-9 Anode for Mercury MerCruiser Alpha One SS (1982-89), Replaces 55989A3, Pack of 2

The Sierra 18-6015-9 Anode is a sacrificial anode built for Mercury MerCruiser Alpha One SS drives (1982-89). Sold as a pack of 2, it protects the outdrive and surrounding metal components from galvanic corrosion caused by electrolysis in salt, brackish, or fresh water. Sacrificial anodes work by corroding in place of more expensive drive components, so they need to be inspected regularly and replaced once significantly worn down, well before they are fully consumed, to keep the protection intact.

This anode is a direct fit for the Alpha One SS drive and cross-references to the Mercury Marine 55989 series part numbers, making it a straightforward swap for boat owners maintaining their own MerCruiser outdrive. Because it ships two to a package, one purchase covers a full anode replacement on a single drive or gives you a spare for the next service interval.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-6015-9
• Product Type: Anode
• Pack Quantity: 2
• Weight: 0.48 pounds
• Fitment: Mercury MerCruiser Alpha One SS (1982-89)

Fitment

• Mercury MerCruiser Alpha One SS (1982-89)

Replaces (OEM)

• 55989A3
• 55989Q9
• 55989T9
• 55989A9
• 55989A4
• 55989

Frequently Asked Questions

What drive does the Sierra 18-6015-9 anode fit? The Sierra 18-6015-9 anode is built for Mercury MerCruiser Alpha One SS drives (1982-89).

How many anodes come in the package? The Sierra 18-6015-9 ships as a pack of 2 anodes, enough for a full replacement service on one Alpha One SS drive.

What OEM part numbers does the 18-6015-9 replace? It replaces Mercury Marine part numbers 55989A3, 55989Q9, 55989T9, 55989A9, 55989A4, and 55989.

How much does the Sierra 18-6015-9 anode weigh? The pack of 2 anodes weighs 0.48 pounds.

Is this an OEM or aftermarket anode? The Sierra 18-6015-9 is an aftermarket anode manufactured to match the fit and function of the Mercury Marine 55989-series OEM anodes it replaces.

Will this anode fit a Bravo drive? No, the 18-6015-9 is designated for the Alpha One SS drive (1982-89); Bravo drives use a different Sierra anode part number.

When should the 18-6015-9 anode be replaced? Sacrificial anodes like the 18-6015-9 should be inspected regularly and replaced once noticeably corroded, before they are fully consumed, so the Alpha One SS drive stays protected from galvanic corrosion.

Why does an Alpha One SS drive need an anode like the 18-6015-9? The anode sacrifices itself to galvanic corrosion in place of the drive's metal components, which is essential protection in salt, brackish, or fresh water.

Can I order the 18-6015-9 as a single unit instead of a pack of 2? The 18-6015-9 is sold as a pack of 2; it is not offered as a single-unit package.

Does the 18-6015-9 cross-reference to Mercury Marine 55989A9? Yes, 55989A9 is one of the OEM numbers the Sierra 18-6015-9 anode replaces.