Story and photography by Capt. Vince Daniello
In 2009 the ABYC adjusted their recommendations so my older meter reflects outdated -.5 to -.7 volts as appropriate for fiberglass boats, not the most up-to-date -.55 to -1.1 readings. The current suggestion for steel is between -.85 and -1.1 volts, and for aluminum between -.95 and -1.1 volts. If you were not able to perform the ohm test described earlier, detach the meter’s lead from the engine and use it to check each bonded fitting. If the voltages all match, the connections between the fittings are sound.
Too Much of a Good Thing?
According to Ward Eshleman, president of Ward’s Marine Electric (www.wardsmarine.com) in Ft. Lauderdale, new ABYC standards (which Eshleman helped draft as an ABYC subcommittee member) stipulate that it is impossible to over-zinc bronze, steel, or aluminum in the marine environment. But sodium hydroxide generated by cathodic current passing through a bonding system will deteriorate wood that is wet where it touchs metal. Wooden hulls and wet wooden backing blocks beneath metallic hardware are particularly prone to this problem. Eshleman’s best advice is to keep wooden boat voltages around -0.55 volts, keep bilges dry, and inspect wood or wooden backing blocks around bronze hardware often.