December 3, 2023

Hardcore Game Fishing

Game Fishing News

When Lightning Strikes

(Photo/Joe Byrum)

By James Cote

Ask any marine insurance adjuster about trends in lightning claims on recreational fishing boats and you will get an earful. During a recent marine insurance seminar, I remarked that without even seeing the boat I could estimate a direct strike to a new 72-foot sportfish could cause more than $600,000 in damage.

What is driving this trend of spiraling lightning repair costs? The answer becomes clear if we compare our modern boats with earlier models such as Ernest Hemingway’s M/V Pilar, a 1934 38’ Wheeler. Obviously, Hemingway had some real problems in his life, but despite his string of bad luck that included getting hit with a mortar, contracting anthrax, breaking an arm, a prolapsed intestine, a car accident, two plane crashes, three self-inflicted gunshot wounds and four wives, there is no record of Pilar ever being hit by lightning.

While the Pilar may have been struck at some point, it likely would have been a “non-event” due to the simple yet robust mechanical grace of the boats from that era. Since the entire electronics package was limited to such things as a two-way radio, magnetic compass, engine distributor and coil (if gas-powered), and maybe an autopilot, there was not a lot for lightning to break.

High-Tech Sportfishing

Contrast the Pilar to the modern sportfishing boat with her array of “mission-critical” electronic equipment, which many of today’s sportsmen are completely dependent on for their fun and games (GPS, radars, chart plotters, depth sounders, fish finders, teaser reels, thrusters, etc.). Everyone knows “that guy” who couldn’t get out of the inlet without his electronics package (hopefully, you aren’t that guy). Couple that with electronic engine controls/steering, remote controlled circuit breakers, air conditioning, refrigeration, toilets, entertainment systems, sea stabilization, sonar, electro-hydraulics, watermakers, etc. and we can see why modern sportfishing boats are so susceptible to lightning damage (much to the chagrin of the insurance underwriters).

Additionally, rapid advances in marine electronics not only render last season’s model obsolete but also drive up lightning repair costs. For example, when a discontinued display screen is damaged, the new model may not be an exact replacement and could require carpentry work or network upgrades. It also does not help when ethically challenged contractors condemn undamaged or repairable equipment and/or overbill, with the captain turning a blind eye to such behavior (I don’t believe such fraud to be widespread, but it does occur).

Another factor driving up lightning repair costs is the proliferation of “connected” boats. NMEA2000, NAVNet, Octoplex, Ethernet and other network systems that connect everything to everything else through touch screens and glass bridges have transformed fishing boat wiring into spider webs that interconnect every component and system. It is easy to see how a voltage spike that would have damaged only a handful of components on a 1980s sportfish now causes sweeping damage. Even center consoles are affected as outboard motors have evolved into complex microprocessor controlled and integrated systems. Isn’t it ironic how the “convenience of connectivity” has also made it so convenient for lightning to do its damage?

Diverting the Strike

Surge Protection Devices (SPDs) are electronic devices that help absorb harmful voltage spikes. SPDs are becoming widely available in several different configurations to accommodate a variety of marine electronics.

Although no lightning protection system can guarantee total protection, the situation is not hopeless. A properly designed, installed and maintained lightning protection system can significantly reduce damage if a few simple rules are followed. However, we should first understand that old-school systems are not intended to protect equipment and toys. In fact, the marine lightning protection rulebooks “ABYC TE-4 Lightning Protection” and “NFPA-780 Standard for the Installation of Lightning Protection Systems” state that the purpose of marine lightning protection is to prevent hazards such as fire, foundering and personnel injuries. Protecting teaser reels and GPS receivers are a secondary concern at best.

I was on a case where a sailing catamaran was hit with real wrath-of-God multiple strikes while the captain was in the cockpit. The sailboat sustained extensive damage to its electronics, but after the captain changed his shorts, he was none the worse for wear. According to ABYC and NFPA the lightning protection system worked perfectly!

Nevertheless, the principles from the old-school systems can be used to help prevent equipment damage. The old saying that a lightning strike cannot be prevented may be true, but a good lightning protection system can divert the lightning energy harmlessly to the water (away from people and flammable materials). This is accomplished by providing the lightning with a better short circuit path to “ground” than the vessel’s wiring offers. This approach can be quite effective as long as a few simple rules are followed (despite lightning not always being that good at following rules).

Rule #1 of Lightning Protection

The first rule is the air terminal (a.k.a. lightning rod), should be the highest point on the boat (it can be a bit more complicated depending on the vessel profile, please seek expert advice). Sportfishing boats with multiple antennae and outriggers can be challenging, but there are usually workable solutions. For example, outriggers can be used as air terminals, if the grounding conductors are properly installed (see below). Also, many sportfishing boats have much longer antennae than needed, which can be shortened or swivel-mounted.

A shaft arc from a lightning strike. (Photo/James Cote)

Rule #2 of Lightning Protection

Next, a #4 AWG or larger tinned grounding conductor should be connected to the air terminal using corrosion-resistant connectors and wiring runs that are as straight as possible. Sharp bends in the wiring and washers between terminal connectors should be avoided. The
grounding conductor must be routed away from all other electrical conductors. This is extremely important, as lightning currents can induce current spikes in adjacent wiring.

A college professor once told me that lightning contains all frequencies “from DC to daylight” as the lightning current goes from zero to thousands of amperes and then back to zero in a split second. This current spike will induce havoc, creating currents in any wires strapped to the lightning grounding conductor. One particular captain was very upset that the lightning protection system he installed did not prevent damage. A post-strike assessment revealed that he had strapped the lightning grounding conductor to the main panel wiring harness. The lesson here is that an incorrectly installed system can be worse than no system at all.

A lightning-damaged IsoBoost due to improper protection. (Photos/James Cote)

Rule #3 of Lightning Protection

Third, the lightning grounding connection “to the water” should be a dedicated submerged metal plate as close to directly beneath the air terminal as possible. This plate may be connected to the bonding system for cathodic protection, but the bonding wires should not be part of the lightning protection system. I had a real face palm moment when I was surveying a motor yacht following a strike. The builder did a splendid job of running a grounding conductor down to the engine room but then connected it to the cathodic bonding system, with the path to ground including the propeller shaft cathodic bonding brushes!

The lightning strike energized the entire cathodic bonding system on its way out, taking out the engine controls and engine room equipment, with arcing evident at the propeller shaft brushes. Strangely, ABYC is just A-OK with using the bonding system and propeller shaft brushes as part of the lightning protection system. My great respect for ABYC notwithstanding, this is a colossally stupid idea on boats with electronically controlled engines and lightning-sensitive electronics connected to the cathodic bonding system.

Externally adhered grounding plates. (Photos/James Cote)

Rule #4 of Lightning Protection

The fourth rule is side flash protection, which essentially means connecting a large metal object directly to the grounding plate. Side flash conductors should be run from metal stays, shrouds, chain plates, deck rails, tower legs, etc. down to a grounding plate to prevent “flashover” to nearby people or equipment. The catamaran captain who had to include a change of underwear with his insurance claim did not feel it necessary to install the recommended side flash conductors. A post-strike survey of the lightning damage revealed that properly installed side flash conductors would likely have prevented much of his damage.

What an air terminal looks like post-lightning strike. (Photos/James Cote)

Other Considerations

The most often overlooked lightning protection system consideration is maintenance. Corroded connections kill the effectiveness of a lightning protection system. Inspect regularly and keep the connections clean, dry and corrosion-free.

Admittedly, it can be challenging to install a perfect marine lightning protection system, especially after market. All of the rules may be difficult to comply with after the boat has been assembled, and we should remember that a poorly or incorrectly installed system can be worse than no system at all. Therefore, installations should only be performed by qualified marine electricians with good lightning protection experience.

Due to the air terminal being too low, this antenna was damaged port-side after a lightning strike. (Photo/James Cote)

Surge Protection

Now, what about those bronze bottle brushes, metal umbrellas and other types of “dissipation arrays” that purportedly prevent strikes through nebulous processes? All I will say about these devices is that a) the laws of physics do not support the claims, b) independent tests have shown these devices to be ineffective and c) I have yet to see meaningful technical data supporting the claims. Nevertheless, if you are a fanboy of these products, by all means install one and let me know how it works out.

Surge protection devices (SPDs), on the other hand, are electronic devices that can absorb/attenuate harmful voltage spikes and are recognized by NFPA, ABYC and UL. The 120-volt power strip connected to your computer is an example of devices that include SPDs to prevent voltage spikes. The exciting news for boaters is that SPDs are becoming available in configurations for 12-volt, 24-volt, antenna and network applications. An SPD can be thought of as a “voltage fuse” and is installed across the input connections of the device to be protected. If the incoming voltage is normal then the SPD behaves as an open circuit. However, if a voltage spike occurs, then the SPD will “short circuit” or “clamp” the voltage down to an acceptable level. Key SPD considerations are what equipment should be protected (i.e., mission-critical, expensive, prone to damage), SPD location, response time, clamping voltage and energy dissipation.


SPDs cannot instantaneously absorb infinite amounts of energy and as such are not a magic bullet, but can be a part of a comprehensive lightning protection system. Multiple SPDs are typically installed to protect various systems (e.g., main switchboard, subpanels, engine electronics, shore power input, helm station, VHF antenna, radar). The great challenge for mariners now is finding SPDs with connections that are compatible with marine systems.

Another key point with SPDs is that modern electronics often have more than one electrical connection point (e.g., power input, network interface, antenna connection). To illustrate, I had an SPD on my desktop computer’s 120-volt connection. Unfortunately, a lightning event took out the computer via the unprotected ethernet connection (facepalm moment on me). I do not believe attaching a bronze bottle brush to the computer would have prevented the damage. Nevertheless, the replacement computer is now safely networked via WIFI, thereby eliminating the ethernet entry port. Converting onboard hardwired connections with WIFI, Bluetooth or optical interface could similarly help prevent an avalanche of lightning damage (example: a solar-powered wind instrument connected via Bluetooth).

After the Strike

How about what happens after a lightning strike? First and foremost, make sure everyone is safe. Then, check to ensure that the boat is not foundering, on fire or in danger of collision. Systems testing may be best left to professionals, as the strike may have damaged critical safety systems. Turning switches on and off is not a lightning damage survey. Electrical, electronic, engine and air conditioning technicians should inspect, test and sign off on their systems.

However, sometimes lightning strikes occur in remote locations where your good seamanship and foresight are all you have. Is there a spare handheld radio with batteries? Is there an engine limp home mode and steering backup? Can you navigate without electronics? If you do have coverage, contact your insurer early on and jointly develop a plan to get the boat to safe harbor.

But if your lightning protection system and your post-strike plan are sound and you stay engaged during the repairs (and are lucky), you should be back on the water in relatively short order. If not, it can be a long painful process.

The post When Lightning Strikes appeared first on InTheBite.

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