Tips from an Unplanned Rewiring


Jamie and I co-author the cruising column for 48° North, a Pacific Northwest regional boating magazine. Our article for November is based on lessons learned while Jamie worked to help our friends on sv Tahina recover from a lightning strike.

Flash, Crack! And Ozone

Tioman Island in Malaysia, with its mountainous interior and great snorkeling was the perfect destination after months in muddy Borneo. At Tioman we reconnected with Tahina, a St. Francis 50 catamaran, and owners Frank and Karen. After a few days of startling reef fish with Tahina’s remote operated vehicle (ROV) submarine, she sailed from Tioman for Singapore and the Straits of Malacca. Then an email from Frank arrived, describing a flash of lightning followed instantly by an earsplitting crack of thunder and the strong smell of ozone. Shocked by the shock, but they couldn’t pause because their anchor windlass spontaneously came to life and began pulling the anchor up!

The strike was probably indirect, inflicting no structural damage, although the missing masthead VHF antenna was an interesting feature. Electrical and electronic devices suffered badly with windlass reversing solenoid and remote, inverter / charger, most LED lights, and all navigation and sailing electronics (from autopilot to VHF) destined for trash bin. Tahina’s plan to cross the Indian Ocean in a few months was suddenly tenuous, so Frank asked me for help getting the boat passage ready again.

After a month of work, without a chandlery for hundreds of miles, Tahina is again ready to cruise. From this, and past, experience I’ve compiled some tips and tricks to help make it easier and safer to manage the mess of wires that end up on most boats. That said, electricity is lethal so understanding electrical hazards and practicing all precautions with 12 volt and AC systems are a must. Always disconnect shore power before doing any electrical work.

Wire organization- If you’re going to have scores of wires aboard, it’s good practice to keep them organized and secure. Often this isn’t done well, but a tangle of wires will macramé together to form a mess that looks darn secure. Problems arise when fishing out a wire from the tangle resembles removing duct tape from someone’s hair. It’s going to hurt and probably require cutting.

Over-bundling- The reverse also happens. Some boats have wires bundled together nicely. Then zip ties are applied every few inches, followed by nylon wire wrap (the stuff that spirals around wires to keep them together) and then finished off with more zip ties. This armor-clad approach does secure wires, but too much so. Anyone tasked with adding or removing one wire from the bundle may well find it easier to sell the boat as is.

Strain relief – All wires must be secure to prevent any pulling force against its terminal connectors (a mechanism for connecting wire at its ends). Wire connections at the top of the mast and wire bundles with small and large diameter wires especially, since the wire weight alone will break any terminal connection.

Chafe prevention –Wires passing through a pulpit, mast, or bulkhead can chafe through their protective insulation quickly. A rubber grommet, length of plastic tubing, or silicone sealant will protect the wire.

Conduit – A conduit such as thin walled PVC pipe is a great way to protect and neaten wires as they snake to and from different areas of the boat. A lack of conduit access holes makes it difficult to run new wires and causes longer than necessary wire runs. Access holes can be cut if the conduit isn’t too full. Using a hacksaw blade, saw with short movements and only deep enough to break through the pipe wall.

Zip-ties – Whether cinched tightly around a wire bundle or used to anchor wires to a fixed point, zip ties are cheap and effective. Sometimes the clipped end can be sharp enough to slice skin, so carefully cut the excess end off flush with a utility knife. Zip ties are nylon and rot after a year two in the sun, so avoid using them for above deck applications such as masthead wire strain relief.

Wire wrap – These don’t really secure wires and are slow to add or remove, but they do protect and bundle wires nicely. They’re best for small bundles that aren’t likely to require changes, such as an engine wiring harness.

Electrical tape – Don’t use electrical tape to wrap wires together because it will leave a sticky mess if removed. Also, shrink tube is a better choice than tape for sealing the wire to terminal connection. Electrical tape is adequate for labeling wires or any number of temporary uses.

Corrosion – Another form of connection problem is corrosion. Quality wire and connectors sealed with heat shrink go a long way to reducing corrosion, but it’s hard to eliminate altogether. I recently discovered that an inline fuse and holder, below decks and dry, developed a little surface corrosion. Even though it appeared minor it was enough to cause electrical resistance and heat sufficient to melt the fuse holder until the fuse blew. Wet areas such as anchor locker, bilge, and above deck locations require inspection and maintenance to ensure wire connections don’t become a problem.

Fuses – As a practical rule, I find the spade type fuses easiest to read the amp rating and to see if it is good or blown. Fuses, unlike circuit breakers lined up on a distribution panel, are wired inline somewhere along the length of the positive wire. Therefore, they can be hard to find. On Tahina, I found an inline fuse installed by the boat builder in the middle of huge wire bundle, all inside of a conduit. It’s a good idea to document all inline fuse locations at the dock instead of when you have a problem on a rough day.

Circuit breakers – A circuit breaker rated for 15 amps on a circuit requiring a maximum of three amps isn’t really providing enough protection. It would take up to five times the circuits required amps to trip the breaker, enough to cause much heat and potentially fire. Match a circuit breakers rating to just above maximum required amps for the devices on that circuit. Alternatively, each device can have an inline fuse with appropriate amperage rating.

Fuse block – A good way to free up circuit breakers and reduce wires to the distribution panel is to use a fuse block. Every device needs circuit protection, but it doesn’t have to be a circuit breaker as long as the device has its own on /off switch. A fuse block enables one circuit breaker to provide power to multiple devices, with each device being protected on its owned fused circuit. For example, a chartplotter, radar, VHF, and sailing instruments are often wired to four different circuit breakers. Instead, connect them to a fuse block and then to one circuit breaker.

Bus bar – The negative bus bar is often overcrowded with wires. Instead, install small negative bus bars in several places around the boat. Negative wires in the area can attach to a small bus bar, which is then connected to the main bus bar with one heavy gauge wire. This greatly cuts down the amount of negative wires running throughout the boat.

A planned wiring upgrade or even simply installing a new device can be challenging enough. With basic knowledge and electrical precautions, it’s not hard to incrementally improve any onboard electrical system to be reliable and easily maintained. An unplanned rewiring halfway around the world with no chandleries for hundreds of miles was an interesting experience. As Totem makes her way up lightning alley, towards Thailand, we really hope to avoid the smell of ozone.

Puget Sound residents can pick up 48° North in boaty outlets, but anyone can read the full issue free online.

4 Responses

  1. I wish I had the chops to write funny like this:”Anyone tasked with adding or removing one wire from the bundle may well find it easier to sell the boat as is.” Allowed me to read a dry, informative story with a smile on my face.

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