Boat lifts have been used in commercial shipping lanes and deep sea ports since late in the 18th century. Today, the modern understanding of a boat lift, sometimes referred to as a boat hoist, is understood to reference a common piece of mooring equipment used for small boats and personal watercraft.
Modern boat lifts are used to lift and hold a boat out of either salt or fresh water. Most often, a boat is driven over straps, beams, a platform, or other mechanisms that sit at or just below the water level. Once in place, the boat lift allows dock employees to raise a boat out of the water for storage, repairs, or removal to a boat trailer for transport.
We know that when you launch or take out the boat at a boat ramp, most of the boat trailer goes in the salt water, with the back wheel of the car just near the edge of water. What happens when you submerge often live 12 volt components into salt water is that you electrify the water around that component causing a process called electrolysis, that eats away at any electrically charged component casing damage at an alarming rate. It won’t short out your system or blow fuses because the water becomes part of the electrical system. What it does do is dissolve copper components throughout the system, even if those components aren’t in direct contact with the water.
The electrolysis begins at the point where the live copper wire is in contact with the water and then travels up the electrically charged wire destroying it as it goes. It’s not an instant process, so launching your boat with exposed electrical components on the trailer will only expose it to a short amount of electrolysis, as the trailer comes back out of the water and the water drys off the process stops. But every time you launch you add more damage until the system fails. This all is not to mention what it can do to trailer brakes.