ELECTRIC OR HYDRAULIC?
Trailer brakes fall into two categories; electric (controlled by a brake control in the tow vehicle) and hydraulic surge (actuated by a special trailer coupler with no control from the tow car). Typically, hydraulic surge brakes are fitted to boat trailers and rental utility trailers.
In the past, boat trailers relied heavily on surge brakes setups because it was thought that the electric brake components mounted in the wheel (the shoes, arms, magnet and related springs and parts) would rust quickly because they are constantly dipped in water when the boat is launched. Today, however, more marine trailer builders are installing electric brake systems because brake manufacturers have started offering corrosion-resistant brake components such as galvanized or stainless steel metal parts coupled with rare-earth magnets.