TOPIC: The Other Mercury

Good story on the development of the Mercury In-line 6

1959 Kiekhaefer Mercury Mark78A Custom Deluxe Outboard



The Other Mercury from Hemmings Motor News
November, 2006 - David Traver Adolphus

According to legend, Carl Kiekhaefer wasn't involved with the design of the inline-six that would make his company's "Mercury" outboards the benchmark for a generation of speed-addled boaters.
The Evolution of the Inline Six, online at www.screamandfly.com , says that sometime in 1955 or 1956 Charlie D. Strang, chief engineer at Kiekhaefer Mercury (the Kiekhaefer name was dropped in 1969), began development of a new engine in secret. Ken Denman from the Antique Outboard Motor Club says that, "He'd been ridiculed by Carl years before, when Charlie had presented him with his new invention, the stern drive."

He worked with the materials at hand, two- and four-cylinder engines that the company already produced. He welded three crankshafts from the twin to create one for the six, and cut two four-cylinder blocks apart to produce a single unit. No magneto? No problem, as plenty of cars had them for sixes. Strang hid the new powerplant from Kiekhaefer until development work had advanced to a point where they could test it on the water. "At first, Kiekhaefer laughed out loud," says Evolution. "When he was done laughing, they convinced him to take it for a test run.
"When he returned to the dock, he is reputed to have said, 'It speaks with authority. Build it.'" The first version, 1957's 60hp, 60-cu.in. Mark75, was cast with the words "Marathon Six" on the side, and in an endurance run in 1958 at the company's secret Florida testing facility, "Lake X," a pair of Mark75s ran continuously for 68 days at an average speed of 30 mph.
Kiekhaefer Marine released the 66-cu.in. Mark78 for 1958, and called it the "Super Marathon Six." With 70hp, it was 40 percent more powerful than the closest V-4 competition from Evinrude or Johnson, and "the introduction of the Mark78 kept Merc ahead of the new three-cylinder, 60hp Scott-Atwater in the 1958 horsepower race," says Evolution contributor Sam Cullis.
Nineteen-fifty-nine, the 20th anniversary of the company, put an "A" into the model for "Anniversary," and introduced the optional Custom Deluxe trim, with chrome and stainless accents, in either the standard Cloud White or, as seen here, in Cloud White and Holiday Red. "The 'square' top styling and stamped aluminum front cover that started on the 78A continued on inline-six Mercs until the very last inline-six Merc was made in 1988. Few products kept their styling so consistent for 29 years," said Cullis.

Known as "Dockbusters," Mark75s and 78s are famous (or perhaps notorious) for their Direct Reverse drivetrains. No existing lower unit that could handle the power of the Mark75 would fit, so, insisting it would be the new standard, Kiekhaefer adopted an unusual technology found on submarines and other very large prime movers: The engine never idles in neutral; as soon as the pilot starts it, the prop starts turning. For reverse, one stops the engine, and using controls at the helm, starts it running counter-clockwise. "From today's perspective, it is difficult to imagine how weak and unreliable starting batteries were back then," says Cullis. "Quite often, by the time a Direct Reverse Merc actually started, the driver had lost track of the throttle position, and the motor roared to life with the throttle much too far open." Ken Denman says, "Inevitably, an inexperienced pilot would get flustered by the constant reverse-start-stop-start-forward jockeying, and would ram a dock."

The engine has ingenious technology throughout: The ignition involves two coils, dual points and a single distributor with two contacts to fire the spark plugs. Later models have a stick at the helm that operates the engine through an offset gate, with microswitches at the detents; and of course, a complicated starter, throttle linkage, water pump and timing gear to operate the engine in two directions.

Mark78As weren't terribly rare in their day (although they're becoming scarce now), and due to their size and characteristics, occupy a specialized niche among collectors. With a $960 list price in 1959 (the pair shown here retailed for as much as a brand-new Nash Rambler 100), they were likely to be well cared-for by the original owners. The 1960s horsepower race and the availability of full gear shifting in 1961 Mercurys, meant that engines from the Dockbuster era were retired after just a few years of use and can be found in good unrestored condition today. "For the most part," said Cullis, "Dockbusters are still ready to complete the remainder of their 68-day reliability run."

Today you can find Mark78s for under $200, with fanatically restored versions showing (unrealistic) asking prices heading toward $4,000. Cullis puts them "third in line behind the highly sought after Mercury 1000 (the first 100hp motor made by anyone) and the 1957 Mark75," and mentions that Mercury never developed any racing parts for them.

Regardless of current interest, Charlie Strang's Kiekhaefer Mercury "Tower of Power" Mark78A remains a big, sophisticated and stylish winner in the outboard horsepower race.

This article originally appeared in the November, 2006 issue of Hemmings Motor News.

Best damn and GOOD LOOKING motors EVER made! Remember a kid 50's and the guy across the lake had a Dock Buster. DAMN that sound hooks me for life! Still think the XS the best decaled Merc made! Even if mine is a Doc built 135, no louvered wrap, STILL looks great! Other pix is my 74 Switzer with new XS. Beast! Came with Blue strip, but went to red when available. Miss that old boat!

good article,,great sounds blue has 100,s orange has 135 s