Galvanization Protection

Maintenance Q & A — March 2001
By Capt. Ken Kreisler

Galvanization Protection

Preventing corrosion, cutting fiberglass cloth, and more.

 More of this Feature
• Part 1: Galvanization Protection, PWC starter problems, bending copper line
• Part 2: Calculating amp-hour ratings, cutting fiberglass cloth, and more
 Related Resources
• Maintenance Q & A Index
• Maintenance Editorial
 Elsewhere on the Web
• Mercury Marine

I’m considering buying a boat equipped with a MerCruiser stern drive and a MerCathode system already installed. How does this work? H.B., via e-mail

The MerCathode system is designed to protect the immersed metal on your boat against galvanic corrosion. As illustrated in the diagram, it consists of a solid-state controller mounted internally and two small electrodes installed on the outside of your boat’s transom below the waterline.

When the system is activated, the corrosion-sensor electrode (B) senses the presence of galvanic current and then automatically directs the controller (A) to maintain a sufficient current to the other electrode (C) to prohibit the transfer of electrons that normally creates galvanic corrosion. The system automatically adjusts for salinity and water temperature as well as for the presence of exposed metal due to abrasion or other factors. The system is powered by your boat’s 12-volt battery, but current draw is very small, so under normal circumstances the chances of the system causing unnecessary drain on your battery should not be a concern. The only drawback is that if power is interrupted due to a dead battery or interruption of the shore-power connection, protection ceases.

For further information, contact Mercury Marine at

The starter on our boat’s PWC has been turning over slowly. What should we check?
P.H., via e-mail

First check your battery with a hydrometer. If the reading is below 1.230, recharge it. If the battery does not take a full charge, you’ll need to replace it. If your battery is okay, inspect your wiring harness for poor contact at the starter solenoid and starter motor, as it may have shaken loose during operation. Also look for corrosion on the terminals and brighten them if necessary.

If you continue to have problems, the causes of which can range from a faulty starter switch to a burned-out starter motor, it’s probably best to call in a mechanic.

In addition, because PWCs are prone to jet-pump restrictions, such a blockage may mask what appears to be a starter problem. Check for weeds, rocks, or other debris that may be locking or binding up the impeller.

So far I’ve been unsuccessful in bending a flexible copper line without kinking it. I don’t want to buy a tubing bender, as I’ll probably have no use for it in the future. Any suggestions?
S.S., via e-mail

Block one end of the tube with tape and fill it with dry sand before bending it. The sand will prevent the walls from kinking. Wash the sand out completely and allow the tube to dry before installing it.

Next page > March 2001 Maintenance Q & A continued > Page 1, 2

This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.

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