• Carry spare parts, such as wire and electrical connectors, fuses, bulbs, engine belts, distilled water for the batteries and engine fuel filters.
• Carry electrical tools, such as crimpers, a wire cutter and a voltmeter.
• Be sure all battery terminals are tight, clean, corrosion-free and sealed against moisture.
• Avoid using wing nuts for battery connections because vibration can loosen them and they are difficult to adequately tighten. Use nylock hex nuts. Loose connections create resistance arcing and heat, and can lead to overheated wires and possibly a fire.
• Check battery water levels if applicable.
• Check battery cables for damage or swelling, which means moisture has gotten under the sheathing and is expanding the insulation.
• Be sure battery switch connections are clean and sealed.
• Never lubricate electrical connections, especially at the battery. Use a corrosion inhibitor (such as the one from CRC Industries) to hermetically seal the connection.
• Batteries in parallel should be the same age, case size and have the same amp-hour or CCA rating to avoid an efficiency-robbing imbalance in the bank. Unless they are relatively new, replace both batteries, even if only one is shot.
• Use tinned buss bars and tinned electrical components only.
• The hole in any ring terminal must match the size of the stud or screw retaining it. Otherwise, the connection can be compromised.
• Check the bonding system for loose, corroded or otherwise high-resistance connections to prevent galvanic and stray current corrosion. This often-ignored system is one of the keys to preventing underwater metal corrosion. Its effectiveness is contingent on good low-resistance connections throughout (no more than 1 ohm between any two parts of the system).
• If the engine or its cooling system uses internal zinc protection, make sure the zincs are replaced when they’re 50 percent (or more) depleted.
• Be sure the batteries have been tested for optimum capacity. Use a digital voltmeter to conduct a simple but effective battery load test. Connect the voltmeter to the battery. Turn on all DC-powered equipment, and then crank the engine — don’t start it. The reading on the meter should not drop below 10.5 volts. If it does, the batteries may need to be replaced or are too small to support the electrical devices on your boat. “If you don’t have an on-board genset, the boat owner really has to ration their usage,” says Ed Sherman of the American Boat & Yacht Council.
• Check all connections for corrosion and tightness, particularly the VHF radio and navigation lights.
• Check wiring for wear, chafing and corrosion; look for green or white residue on wires — that is corrosion.
• Make sure wiring has strain relief to prevent the connections from being stressed if the wire is stepped on or pulled on, or otherwise loaded.
• Check the VHF antenna and its connection for cracks, chips or other damage.
• Owners of boats about 30 feet and up who have added electrical equipment should consider a larger alternator. An alternator runs hotter at full capacity, causing it to fail prematurely.
• On boats with multiple batteries, be careful not to shut the battery switch off while the engine is running to avoid possibly blowing an alternator diode.
• Turn off all power before starting any work.
• Use a component’s recommended breaker or fuse sizes.
• Never tap into other wires; start the connection at a positive terminal block and circuit breaker, and a grounding bus.
• Keep a record of any new wires or cables installed; use zip ties for a clean, neat installation.
• When it comes to wire and cable, the higher the gauge the better.
Sources: Erik Klockars, Soundings technical adviser; Steve D’Antonio, technical editor of PassageMaker magazine and owner of Steve D’Antonio Marine Consulting; Dave Laska, owner of L&L Electronics; and Ed Sherman, director of curriculum development and delivery for the ABYC.
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This article originally appeared in the September 2011 issue.