How to Replace Zinc Anodes on Alpha One

by Will Charpentier

The Mercury Marine Alpha One is a 300-horsepower brute when it's in water; Mercury describes it as a "low drag hydrodynamic torpedo." It can suffer the effects of galvanic corrosion, though, and Mercury Marine's warranty information on the Alpha One is specific about controlling corrosion, saying, " It is the owner's responsibility to ensure that all necessary anti-corrosion devices are in good working order and are providing adequate protection." This means replacing the five zinc anodes resident on the motor as needed.

1. Use your adjustable wrench to attach the plate zinc anode to the top front of the plate on the lower unit with the bolts and lock washers provided. This is Mercury part number 821629.

2. Use your screwdriver to attach the gimbal zinc anode mounting plate to the bottom of the gimbal plate on the front of the motor. Screw the anode to the mounting plate. This is Mercury part number 821631 and includes the mounting plate.

3. Use the screwdriver and the screw provided to mount the trim tab anode on the bottom of the rear edge of the trim tab. The rounded portion of the zinc (Mercury part number 762145) should face downward.

4. Bolt the two-part trim cylinder anode (Mercury part 806189) around the extended ram of the trim cylinder using the four bolts provided. The zinc should rest on the face of the ram.

5. Remove the prop by bending the retainer tabs off the top of the prop retaining nut. Use your adjustable wrench to attach the Mercruiser Alpha One bearing carrier zinc anode (Mercury part number 806105) to the face of the bearing tube (bearing carrier assembly) with the bolts provided. Return the prop to the shaft, replace the prop retaining nut and bend the retaining tabs back over the top of the nut.

Items you will need

  • Alpha One zinc anode kit with fin
  • Adjustable wrench
  • Screwdriver
  • Sandpaper
  • Wire brush

Tips

  • Change all the zincs as soon as any one zinc on the motor is 50 percent gone.
  • Before installing a zinc, hit the spot where the zinc will be installed with sandpaper or a wire brush to insure a good contact between the zinc and the metal it's protecting.
  • Make sure you're using the right zincs for the waters you cruise: saltwater anodes are made of zinc or aluminum. Freshwater anodes are made of aluminum or magnesium.

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.

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