Mercury – Aluminum Trim Tab Anode | Corrosion Protection & Steering Aid | Cast Aluminum | 31640T4

Overview

Corrosion is one of an engine’s biggest enemies, and the Mercury Marine 31640T4 Aluminum Trim Tab Anode is built to stop it in its tracks. Designed for Mercury and Mariner 30–200HP outboards and MerCruiser sterndrives (except Bravo), this OEM anode protects your lower unit from galvanic corrosion while also providing a small hydrodynamic trim force to help balance steering. Made from high-quality cast aluminum, it works in both fresh and saltwater, lasts longer than zinc, and installs easily with standard tools.

Key Features

• Purpose: Protects your gearcase and drive housing from galvanic corrosion while aiding steering.
• Material: Constructed from cast aluminum alloy that meets MIL-A-24779(SH) military specifications.
• Design: Doubles as a trim tab, reducing steering torque and helping maintain straight tracking.
• Performance: Works efficiently in fresh, salt, or brackish water, offering longer protection than zinc anodes.
• Ease of Installation: Quick replacement using common tools; check prop clearance after installation.
• Compatibility: Fits Mercury/Mariner 30–200HP outboards and MerCruiser sterndrives (excluding Bravo models).

Engine & Boat Compatibility

• Designed for Mercury and Mariner 30–200 horsepower outboards.
• Fits all MerCruiser sterndrives except Bravo drives.
• Commonly used on pontoons, fishing boats, cruisers, and sport runabouts.
• Performs in both freshwater and saltwater conditions.

Performance & Practical Benefits

The 31640T4 anode protects your engine by acting as a sacrificial metal, attracting corrosion away from your drive components. Its hydrodynamic design also helps stabilize steering, keeping your boat tracking straight and smooth. Once installed, it begins working immediately to shield your gearcase, exhaust housing, and mounting hardware from costly damage caused by electrolysis.

This aluminum alloy anode lasts up to 50% longer than zinc, making it the smart choice for mixed or saltwater environments. It’s easy to replace — just check it a few times a season and swap it out when heavily pitted.

Why Buy OEM

Aftermarket anodes often use alloys that don’t meet marine-grade standards, meaning they wear unevenly or fail to provide full protection. The Mercury 31640T4 is a genuine Mercury Marine part, tested and proven for durability, performance, and precision fit.

Mercury’s OEM anodes meet the same specifications used in new-engine production, ensuring the correct alloy composition and corrosion rate. When you install an OEM anode, you’re protecting your entire drive system with the exact material your engine was engineered to use.

FAQ

Q1: Which engines does this anode fit?
It fits Mercury and Mariner 30–200HP outboards and MerCruiser sterndrives, excluding Bravo models.

Q2: What’s it made from?
It’s made of cast aluminum alloy meeting MIL-A-24779(SH) standards for corrosion resistance.

Q3: Can it be used in both fresh and saltwater?
Yes — aluminum anodes perform better than zinc in both environments.

Q4: How often should I replace it?
Inspect it regularly and replace it when it’s about halfway worn or heavily pitted.

Q5: Why choose OEM over aftermarket?
Mercury OEM anodes guarantee correct alloy composition and fit, offering the best protection for your engine.