first 6-cylinder engines featured "direct reversing". Instead of a lower unit with forward, neutral and reverse gears, its lower units were more compact, with only drive and driven gears, and no submerged shift mechanism required. Reverse was selected by turning off the engine and restarting it in opposite rotation, and neutral by simply switching off. Mark 75s, like many of their smaller brethren, were available in an "H" (high speed) version. Many of these large H engines sported open headers for competition and produced 90 horsepower from 60 cubic inches. Two totally stock Mark 75s set a world endurance record on Lake X, running 50,000 miles at an average of 30.3 mph, while being re-fueled on the fly. The boats were stopped only for driver changes and standard maintenance. After the record-setting run was completed, the motors were torn down and inspected for wear. They were found to be well within factory tolerances. For 1958, an enlarged version of this engine was introduced. The new "Mark 78" had 70 horsepower with 66 cubic inches of displacement. No "H" version was offered. Also in 1958, a stock Mark 75H set a new world speed record for outboard motors, of 107 mph. NASCAR racing Kiekhaefer decided to promote his company by owning a NASCAR and AAA team. The team dominated NASCAR Grand National (at one point winning 16 straight races), even though it only competed in 1955 and 1956. The team won the 1955 and 1956 NASCAR championships with drivers Tim Flock and Buck Baker. One of Kiekhaefer's innovations was using dry paper air filters, which are still standard in automobiles today. 1960s When Kiekhaefer Mercury's top-of-the-line, 80 horsepower (74 cubic inch) model "Merc 800" was introduced for 1960, direct reversing as standard equipment was optionally replaced by full forward, neutral and reverse gear shifting, as on Mercury's 2- and 4-cylinder models, and "thru-hub" exhaust was introduced. Previously, as with other outboard brands and Mercury's smaller models, exhaust exited from a chute at the rear of the cavitation plate above the propeller. Thru-hub exhaust was claimed to be more efficient by omitting the added drag of an exhaust chute, and using the low-pressure area necessarily created by the gear housing and propeller moving through the water to assist in exhaust evacuation. Over the next several years, thru-hub exhaust became a standard feature of all Mercury models, and later was adopted near industry-wide