MerCathode Controller Assembly – Fits Mercury/Mercruiser Sterndrives (Replaces 42600A09)

$150.10 $240.00

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This MerCathode Controller Assembly is a Gen III unit for Mercury/Mercruiser sterndrives and outboard engines, designed to protect underwater aluminum parts from galvanic corrosion.

It is a direct replacement for Mercury part numbers 42600A09, 42600A3, and 42600A5.

Installs as a solid-state electronic controller.
Connects directly to your vessel's 12-volt electrical system.
Provides enhanced protection with minimal current draw.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number	Notes
Mercury	42600A09	Current Part
Mercury	42600A3	Superseded by 42600A09
Mercury	42600A5	Superseded by 42600A09

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This controller is designed for a range of Mercury/Mercruiser sterndrives.

Brand	Model	Rated HP	OEM Part No.	Notes
Mercury	R, MR Drives	Various	42600A09	Sterndrive
Mercury	Alpha One	Various	42600A09	Sterndrive
Mercury	Alpha One Gen II	Various	42600A09	Sterndrive
Mercury	Bravo Drives	Various	42600A09	Sterndrive

Technical Specs

Product Type: Galvanic Corrosion Protection System Controller
Installation: Solid-state electronic controller
Connection: 12-volt electrical system
Housing Color: Black with blue decal (Gen III)
Dimensions: Length: 10.0 cm, Width: 9.5 cm, Height: 4.6 cm
Weight: 0.09 kg (0.20 lb)
Fitting Type: Direct electrical connection

What’s in the Box

1 x MerCathode Controller with Blue Decal (42600A09)

Installation Notes

This Gen III MerCathode controller connects to a 12-volt electrical system to automatically protect the sterndrive from corrosion. It provides enhanced output for underwater aluminum parts with minimal current usage. For certain saltwater applications, it can be connected in parallel with 98869A14 MerCathode systems.

Troubleshooting & FAQ

How does the MerCathode system work?

The MerCathode system provides active protection against galvanic corrosion. It operates off your boat's 12V battery, supplying a small, controlled electrical current to the sterndrive's underwater metal components to counteract the natural electrochemical reactions that cause corrosion in fresh or salt water.

Is this controller compatible with my older MerCathode system?

This Gen III controller (42600A09) supersedes older models 42600A3 and 42600A5. It's designed for use with R, MR, Alpha, and Bravo series drives. Always verify your specific part number before ordering.

What are the signs that my MerCathode controller has failed?

Common signs include accelerated corrosion or pitting on the sterndrive's aluminum housing, anodes being consumed unusually quickly, or no electrical output from the controller when tested with a multimeter. A non-functional controller leaves your drive unprotected.

Can this single unit be used in all water conditions?

While this controller provides excellent protection in most environments, some saltwater applications may require additional protection. In such cases, this unit can be connected in parallel with a 98869A14 MerCathode system for increased output.

What is the difference between OEM and this aftermarket part?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

What are your shipping speed and cost?

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

What warranty and return policies apply?

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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