Of all the natural phenomena that we run into out on the water, lightning may be the most worrisome. A direct strike can blow a thru-hull right off the boat creating a gaping hole, it can fry your electrical panel and battery bank and it can start a fire.
Even near misses can create a mess inside marine electronics and the autopilot, or in the alternator and starter motor on your engine, or it can blow up an inverter-charger.
Lightning works in mysterious ways so you can never predict where it will go and what damage it can do. That means precautions have to include just about everything from bow to stern and from the top of a radar dome to the bottom of the keel.
The most essential and basic precaution that should have been taken care of by the boat builder is the grounding system. This can be via Dynaplates on the boat’s bottom or a simple bonding of all thru-hulls, the engine or engines and the generator with heavy gauge wire. Every boat owner should check to make sure that one way or the other the boat is grounded effectively.
When a lightning storm has been forecast and you can see it approaching on radar, there are several simple precautions to take to minimize damage.
If you have a stove with an oven or a microwave oven on the boat, these can act as Faraday cages and will protect VHF radios, hand-held GPSs, cell phones and other small electrical devices.
Shutting off as many electrical instruments as possible and closing circuit breakers and vacuum switches will help to isolate any damage from a strike and prevent systemic damage. This will be difficult if you are underway but even a partial shut-down will help.
And then, there is the aftermath of a lightning storm. Even if you were not hit directly, loose energy in the sky can introduce gremlins in strange places inside your boat. So, you need to run through a checklist to see what is working and what is not.
BoatUS says that American boater’s have a one in a thousand chance of being struck by lightning every year, more if you are in Florida, so be prepared. It can happen.
Here’s a good article on lightning strikes, before and after, in Practical Boat Owner. Read more.
