How to Attach Zincs to a Fiberglass Boat

The term "zincs" is a common reference to the sacrificial anodes attached to metal parts on the outside of a boat hull. Because water acts as a conductor for electricity, anything metal under the waterline is subject to corrosion. Sacrificial anodes, or zincs, are made from the weakest (least noble) of metals so that corrosion attacks them before the harder metals, thereby sacrificing themselves so that important equipment like outdrives survive. Attaching zincs to the specific areas of a fiberglass boat where they are needed is a simple process that should be a part of anyone's regular maintenance schedule.

• 1

  Buy the type of sacrificial anodes that fit the type of water your boat resides in the most. The three main types of "zincs" are made of the least noble metals so they are weak enough to crumble under the effects of corrosion and attract electrical impulses to them. They are zinc, magnesium and aluminum. Magnesium is the weakest and should be used in the least corrosive atmosphere, such as freshwater rivers and lakes. Zinc is the middle strength anode that is used in mildly corrosive waters, such as brackish waters where fresh and salt water meet. These areas are river inlets attached to bays and open ocean salt water. Aluminum is the strongest of the anode materials and used in salt water ocean waters.

• 2

  Remove old zincs on the outdrive, if applicable. Use a socket wrench to remove the bolts on the anode at the front on top of the ledge of the lower unit. Use a socket wrench with an extender to reach down the thin slot on the side of anodes that surround the hydraulic shafts on either side of the outdrive. Remove the plug on the top of the rear outdrive and drop the extender into the shaft to remove the nut inside. Drop off the round disc anode underneath the ledge of the outdrive above the prop.

• 3

  Replace all of the sacrificial anodes on the outdrive. Use new bolts, nuts and locking washers that come with the anodes. Discard old nuts and bolts. If the outdrive is new and there are no existing anodes, install new ones in the above areas using predrilled mounting holes as a guide.

• 4

  Use a prop tool to remove the large prop nut from the center of the propeller. Use the pointed end of the prop tool to lift the locking tabs on the tab ring surrounding the prop shaft and remove the tab and locking nut. Pull the prop off of the shaft and use a socket wrench to remove the nuts on the prop anode around the prop shaft. Lift off of the shaft and replace or install if no previous anode exists with a new anode and replace the prop by reversing the removal process.

• 5

  Use a socket wrench to remove hull attached anodes on fiberglass boats with inboard motors where only the prop protrudes from the hull, or sailboats with metal through-hull appliances. Replace with new anodes and bolts.