Marine Corrosion Solutions         (530) 926-4000

Model 620A - Installation and Operating Instructions

Installing The Anode

  1. The anode should be located on the transom or under the hull depending on the type of drive to be protected and the mode in which the vessel will be operated. Generally, for boats with stern drives, large outboard motors and small jet drives, regardless of how they are operated, the anode should be mounted on the transom. For larger jet drives, sail drives and other aluminum drives that are totally immersed, the anode should be mounted under the hull. Another factor that should be considered is the boat’s mode of operation. Most recreational boats spend a high percentage of their lifetime at the dock or on a trailer so mounting the anode on the transom is acceptable. Also, trailered boats risk damage to any devices mounted under the hull during launching or retrieving operations. 
    Commercial boats and boats that make long passages are typically underway a much higher percentage of their lifetime. In order for the cathodic protection system to provide protection during the times when a boat is underway, the anode should be located under the hull.
  2. The anode can be installed on either side of the drive on the transom of single drive boats but should be installed between the drives on twin drive boats. In either case, the anode should be located well below the water line. If the anode is to be mounted under the hull, it should be located near the drive(s) to be protected.
  3. The minimum distance between an anode and the system reference cell is twelve inches (12").
  4. If the boat is to be operated in low salinity (fresh) water, install the anode between six and twelve inches from the drive to be protected.
  5. Install the anode and route the anode wire so that it will remain clear of any standing bilge water.
  6. Drill a hole at the anode location of sufficient diameter to provide clearance for the anode stud. Use Boat Life – Life Caulk one part polysulfide rubber caulking compound to bed the anode assembly.  Apply the bedding compound liberally, especially around the stud.  Insert the anode wire and stud into the drilled hole.  Have an assistant apply the bedding compound around the stud on the inside of the hull and install the round nut.  !CAUTION! Tighten the nut by hand only.  Do not use any type of tool to tighten the nut.
  7. !CAUTION! The anode wire carries positive electrical current. Be careful to route the anode wire in a manner that will insure that it will not be damaged by normal use of the boat. Good electrical wiring practices should be followed. Refer to the ABYC D.C. Electrical System Standards for recommendations for safe electrical wiring practices.
  8. !IMPORTANT! If the system is being installed on a metal hulled boat – either steel or aluminum – prior to installing the anode a 1/8” thick epoxy extended dielectric shield coat must be applied at the anode location.  This barrier coating is required to protect the hull from the strong electrical field that is created near the anode.  It must extend to at least twelve inches in all directions beyond the anode assembly.  For transom mounted anodes, the epoxy does not need to extend above the waterline.  Use Intergard 822 epoxy mastic to make this barrier coating.  The epoxy barrier should be applied before installing the anode.  Do not use an epoxy fairing compound or any epoxy that has had fillers added.  Follow the instructions supplied by the manufacturer for proper application.  This epoxy compound should be applied directly over the epoxy barrier coat (epoxy primer) that has been applied to the bare aluminum hull according the manufacturer’s application specifications.  It should not be applied over antifouling paint !CAUTION! Application of the epoxy barrier coating is absolutely required for successful operation of the system.  Failure to provide the extended dielectric shield can result in significant corrosion pitting damage to the hull shell plating in the immediate vicinity of the anode.


  1. The same criteria relative to a boat's drive type and mode of operation as discussed above for locating the anode should be used to determine the proper location for the reference cell.
  2. If the boat is to be operated in low salinity water, install the reference cell as close as possible to the drive to be protected. Do not allow the reference electrode to touch the drive structure.
  3. The reference cell should be located on the opposite side of the drive from the anode in transom installations. In any case, the reference cell should not be located closer than twelve inches (12") to any anode.
  4. Drill an appropriate hole for clearance of the reference cell stud and insulating sleeve. Cut the sleeve slightly shorter than the thickness of the hull. Apply one-part polysulfide rubber bedding compound to the fiberglass electrode shield making sure that the compound is in contact with the stud threads. Slide the insulating sleeve over the stud until it contacts the fiberglass shield. Insert the stud through the hole drilled through the hull until the bedded shield is against the hull. Install the bedded 5/8” thick poly washer on the stud on the inside of the hull, then the stainless washer and the nut. Tighten the inner nut while holding the reference assembly on the outside of the hull. An accompanying drawing shows details of the reference cell installation.
  5. Route a #14 AWG green marine grade D.C. primary wire from the reference cell to the #5 position on the controller terminal block.


  1. The monitor is designed to be installed in the boat's instrument panel. Like the other instruments, it monitors the performance of the system of which it is a part -- in this case the cathodic protection system.
  2. Drill a 1 1/8” hole at the selected location in the instrument panel.
  3. With the monitor mounting spring and keeper removed, insert the instrument through the hole. Slide the mounting spring and keeper over the signal cable onto the instrument housing. While holding the instrument, press the keeper to the appropriate retaining slot and rotate it 90 degrees. Make sure the raised locking tabs have snapped into their locking slots.


  1. The monitor signal cable is five feet (5’) long. The controller must be installed at a location that will allow this cable to be plugged into the controller. Try to locate the controller where it will be relatively easy to route the various wires to it that are needed to connect the system.
    !CAUTION! Do not install the controller where it will be exposed to weather or water splash. If the controller must be installed in a location where water splash is possible, always mount the controller with the terminal strip and monitor header pointed down.
  2. After mounting the controller at the selected location, plug the monitor signal cable into the receptacle on the controller. This plug is polarized so it cannot be plugged in incorrectly.
  3. Strip the insulation on the green reference cell wire 3/16” and insert it into the #5 position of the controller terminal block. The jaw of the terminal block position that will receive a wire must be opened before attempting to insert it. To open a terminal jaw, press the white lever handle down until the clamping jaw opens. Insert the wire and, while holding it in position, release the lever. The wire should now be locked into the terminal block.
  4. Route a red #14 AWG D.C. wire from the D.C. distribution panel to position #4 of the controller terminal block. This wire should be connected directly from the D.C. positive buss through either a panel mounted or an inline two-ampere fuse. This wire should not be connected to a circuit breaker. If there is a battery disconnect switch between the D.C. distribution panel and the battery, the D.C. positive feed to the controller should be connected directly to the battery positive output, again through a two-ampere fuse at the battery end.
  5. Route a black #14 AWG D.C. wire from the engine negative terminal (as defined in the ABYC D.C. Electrical System Standards) or if not available, the D.C. negative distribution buss or battery negative terminal to the #2 position of the controller terminal block.
  6. Route a yellow #14 AWG wire from the controller terminal block position #3 to the drive housing(s) that are to be protected by the controller.
  7. Connect the anode wire to position #1 of the controller terminal block. If this wire must be extended, use red #14 AWG wire. Solder the splice and insulate the splice area with heat shrinkable tubing. Remember, this wire carries positive electrical current.

620A installation diagram.


  • The anode, reference electrode and the metal structure to be protected must be immersed in water in order for this system to operate. Therefore, when the boat is out of the water either on a trailer, in dry storage or in a yard, the system is non functional even if the electrical power to it remains on. When the boat is out of the water or any of the above mentioned elements of the system are not immersed in water, the indication displayed on the monitor is meaningless and the system is non functional.
  • The drives on boats that have a transom mounted anode and reference cell, for the reasons discussed just above, will not be protected by the system when the boat is on plane and the transom is dry. On recreational boats, the drives will be subject to little to no corrosion attack because these boats are under way a relatively low percentage of the time. The indication of the monitor instrument, as mentioned, will be meaningless during the periods when the anode and reference electrode are out of the water.
  • Under all other operating conditions the monitor instrument green LED indicator should be lighted. If power is available to the controller and the drives, the anode and reference electrode are all under water, and either of the red LED indicators are lighted, there is a system fault. This fault could be a failure in the controller or controller wiring, or more likely an electrical fault in the boat’s D.C. electrical system or A.C. shoreline electrical system.
  • If a system fault indication is observed contact the Electro-Guard engineering department at the numbers listed below for assistance in correcting the problem.

Mounting Detail, Reference CellMounting Detail, Permanent Anode


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