In Our Wake: The 50,000-Mile Marathon

The Granddaddy of all engine endurance tests happened in 1957. It’s still an almost unbelievable milestone today.

Back in 1957, a mercurial and enormously talented engineer named Carl Kiekhaefer launched an audacious endurance test on what was at the time, a new and radical outboard engine. The two-stroke Kiekhaefer Mercury Mark 75 was a 60-horsepower in-line six. Clad in a chrome cowling, it was tall, but small and light, displacing only 59.5 cubic inches (.948 liters) and weighing 168 pounds. Like the ground-breaking Chevrolet 283 V8 of the same year, the Mark 75’s three carburetors inhaled enough misted gasoline to generate one horsepower per cubic inch—the most powerful outboard ever offered, by 20 horsepower.

Earlier that year, Kiekhaefer had purchased a 1,440-acre cypress and moss shrouded parcel 30 miles south of Orlando called Lake Conlin. Here, at his now top-secret “Lake X” testing facility, and supervised by the United States Automobile Club, he planned to run a pair of stock Mark 75’s 50,000 miles. At 7 a.m. on September 11, a secretive crew set to circling a 5.5 mile course with a pair of runabouts: “Through good weather and bad, five-foot waves, heavy fog and tropical storms,” said the narrator in an epic newsreel on the event.

Fueling and changing drivers every four hours (four on, eight off) was precarious: leap from a 55-gallon drum-roofed fuel boat (filled with a 20:1 mix of Amoco unleaded and Mercury Quicksilver oil) onto the 17-foot runabouts while they were roaring along. Cigarettes dangled from lips. Life jackets were disregarded. Headlights were changed by a crewman draped across the bow at 30 miles an hour. During downtime, you fished for bass or wrangled armadillos barehanded. One morning’s logbook records: “Sighted alligator dead ahead. No time to take evasive action. Felt solid thump. No damage to boat or motor. Damage to alligator unknown.”

On October 15, at 6:45 p.m., the boats were trailered at 25,003.03 miles. They had consumed 3.9 gallons per hour, returned 7.9 miles per gallon and averaged 30.2 miles an hour. After a USAC tear down in Sarasota revealed they were essentially still good as new, they were reassembled with no new parts. Testing continued at 10 a.m. on November 20th.

At 5:03 p.m. on Christmas Eve, the drivers crossed the finish line with 68 days, 18 hours and 51 minutes of motor runtime. Mercury had circled the earth—twice.

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This article originally appeared in the June/July 2024 issue of Power & Motoryacht magazine.

Source: https://www.powerandmotoryacht.com/column/in-our-wake-the-50000-mile-marathon