Mercury Marine has agreed to return to the central Florida lake that became part of its legend. The freshwater lake was a secret testing ground for the 80-year-old engine builder from 1957 until 2004. Launched by Mercury founder E Carl Kiekhaefer, Lake X was designed to be the most secretive marine testing facility in the world, with 12,000 acres of land and 1,440 acres of water.

Officially named Lake Conlin, Lake X was surrounded by a barbed-wire fence and snake-infested foliage. Mercury built in dormitories, kitchens and an observation platform and then manned it with boat drivers and engineers from its headquarters in Fond du Lac, Wisconsin. It allowed the engine builder to test new products in secrecy from the prying eyes of its then-rival OMC during the winter.

Lake X was long used for performance tests of Mercury-powered boats, R&D, new product testing and endurance validation. A visit by IBI in 1998 included witnessing a well-known ski-boat builder testing a possible sterndrive configuration that never made it to market.

Its most famous PR event was a 50,000-mile endurance run, with two boats running continuously on a closed 5.8-mile course, 24 hours a day, seven days a week.

“Returning to Lake X is an opportunity to build an immersive brand experience around that heritage and capitalise on the popularity of the Mercury brand,” says Michelle Dauchy, Mercury’s chief marketing officer, in a statement. “We have been able to host customer and media events as well as take advantage of the lake to test product.”

The secret location in Osceola County is roughly three miles long, one-mile wide and nearly six miles in circumference.