To Bond—Or Not to Bond?

the fastenings—don’t crank on them too hard. Masking around the perimeter of the light (and around the base of the light itself ) will make a neater job when you wipe off the excess adhesive and remove the tape. Finally, squirt sealant into the wiring holes from inside the boat, too, to keep moisture from seeping into the core through the back door.

Macris Industries has a unique way of attaching their MIU Series lights to the hull: Instead of fasteners through the body of the light, which can create stresses in the composite polymer, and crack it if the screws are overtightened, company President Harrison Macris devised carbon-fiber clamps that mount to the hull with adhesive and mechanical fasteners. There’s a clamp at each end of the light, which “floats” between the clamps on a bed of 4200. These low-drag lights are less than a third of an inch thick and can be mounted “almost anywhere on the boat,” according to Macris. MIU Series lights are made from polycarbonate billets machined on the back side to fit the LEDs and associated components; the front of the billet is laminated with a hard, slippery polymer surface that resists scratching and marine growth.

(A word to the wise here: Carbon fiber—graphite—is electrically conductive, so it can create galvanic corrosion when in contact with metal in salt water. But since it’s near the top of the anodic scale—almost as corrosion-resistant as gold!—any corrosion will most likely take place in the metal, not the carbon fiber. So use Type 316 stainless steel for maximum corrosion resistance when fastening the Macris carbon-fiber clamps.)

Through-hull style lights are harder to install, of course, since they need bigger holes cut into the hull—for example, Aqualuma Gen 4 18 Series lights need 3-inch holes to fit their polycarbonate housings. And this means taking serious steps to protect coring from water intrusion; relying on adhesive isn’t gonna do it. Instead, dig out the core around the hole and replace it with epoxy putty before installing the through-hull. This is the proper way to install any fixture or fastening through cored laminate. It adds a lot of work and, if the yard’s doing it, expense, so almost nobody does this for small holes. But it’s the right way. If you hire the yard to install a through-hull light, make sure they do it properly (I’m not saying yards cut corners, but I’m not saying they don’t either). And bronze housings should be connected to the boat’s ground system. (See “To Bond—Or Not to Bond?” on this page.) COLOR ME DISCO! Maybe one color is not enough for you. Lumishore SurfaceMount Color Change lights use a combination of red, green, blue, and white LEDs to produce the full color spectrum in each light’s output. Using a control unit, the skipper can select a preset color, or let the LEDs run through the whole rainbow. Connect the yacht’s sound system and the lights become a disco inferno, changing colors to the beat of the music.

Macris Industries’ MIU Chroma lights (they’ll be available this summer) use what the manufacturer calls Dynamic Pixel Control to create a similarly outrageous light show. Each LED in a Chroma light can change color, controlled by a mini-computer that, in turn, takes its instructions via a smartphone. The Chroma light can change colors randomly, do a “wave” through the color spectrum or, by daisy-chaining multiple lights, turn the stern of your vessel into a Star Wars- worthy light show. It’s a long way from simply luring a fish onto the hook. And hey, the dockside dollies won’t be able to resist. Some underwater lights live in bronze housings, which most manufacturers recommend connecting to a boat’s bonding circuit. Generally, the ABYC also recommends bonding metal underwater fittings in fiberglass hulls. Some experts disagree, saying that if an underwater fitting is electrically isolated, bonding is not only unnecessary, it creates galvanic issues where none existed. If you have a wood or metal boat, the question is even more complex, and plugging into shore power can create even greater problems—although bonding helps prevent electric shock from errant AC, too.

Lumitec makes surface-mount underwater lights in both bronze and aluminum housings. The installation instructions say not to bond the lights. An engineer at the company said that poorly engineered bonding systems aboard a boat, or stray current in the water around said boat—a common situation in marinas—can result in corrosion in bonded fittings, but won’t affect unbonded ones. Rather than go with bonding, Lumitec provides fasteners—silicon bronze for bronze lights, chrome-plated stainless steel with insulating shoulder washers for aluminum—that won’t react galvanically with the metal housings of their lights.

I asked an ABYC technical specialist about this. He said ABYC standard H-27 applies to “through-hull pipe fittings, drain plugs, and seacocks,” but not through-hull transducers and underwater lights. Anything electrical would fall under Standard E-11, he continued, but there’s nothing specific for underwater lights there, either, and the ABYC bonding recommendations are for throughhull fittings intended for water flow, not “energized thru-hulls.” The specialist recommended following the manufacturer’s instructions.

My advice? Consult with a certified galvanic corrosion technician. He can check your situation, test your bonding system, and locate stray currents around your boat. It’s cheap insurance against corrosion.