by Chuck Petersen
A great engineer in his own right, Carl Kiekhaefer developed the historic KG-4 two cylinder motors that dominated stock outboard racing in the late 1940s. These full-jeweled or roller bearing 20 cubic inch models were light and very efficient even by todays standards. In 1949, two of these models were effectively stacked together to make a 4 cylinder in-line 40 cubic inch model using the same pistons, rods and bore size to form a true engineering marvel. The KG-7, later Mark 40 models would set speed records and distance Mercury from their primary OMC competition in the performance category.
In 1956. an equally brilliant engineer, Charlie Strong, began to develop the historic in-line 6 cylinder model. Carl was so involved in auto racing at the time that Charlie had to operate a secret development program on the side that would ensure that Mercury continued to dominate the horsepower outboard race. Working at night, Charlie nutted up a 6 cylinder prototype by sawing 2 four cylinder blocks into two three-cylinder sections. These were welded together and mated with 3 two cylinder crankshafts similarly welded out of bootlegged parts. The package was completed with the help of Edgar Rose, who made an ignition
system using automotive style components. According to Mr. Strong, We finally put it on a boat and took Carl down to see it. It was pretty tall. He got in the boat and took one run up and down the river. He came back and said, It speaks with authority, lets build it.
That was the decision process. Nine months later, the Mark 75, 60 cubic inch model was introduced to the public.
Until the advent of V-6 OMC models in the late 1970s, this motor, eventually reaching 150 HP in stock trim, would dominate performance outboarding.
I remember the black 100-150 HP versions of the early-to-mid 1970s as the speed kings of the Fat Four. OMC 75-IOO HP models of the day are still around; I rarely see a true vintage in-line 6 Merc in service. I will ignore for the moment the fact that the 1957-61 Mercs had dysfunctional direct reverse shift systems. What about the 1962 and on full shift models? I restored a 1962 white 70 HP Merc 700 that really ran well with little fuss. My best guess is the fact that the tall tower of power suffered in two areas. First, motors stored for long periods tended to drain oil and rust bearings on the crankshaft over time. Second, the points and condensers on the outboard mounted magnetos were hard to replace, requiring special factory tools. Newer versions sported a more sophisticated electronics package and are still seen in service.
The V-6, or Black Max, eventually replaced the in-line completely. I miss the look and the sound of the original. I would also encourage restorers to consider using vintage plants on boats requiring 60-100 HP, i.e. 16 foot and up lapstrakes. The old beasts are heavy and require patience to restore, but are still fairly easy to come by and very reliable once restored.
I was excited to attend the 2005 Antique Motor boating symposium in Newport News, Virginia in April. The last time l was able to attend was with my Dad in 1997 for the Garwood themed event. I still remember Todd Warner taking part in the Garwood vs. Dodge debate. I was happy to be there again with my dad and to see fellow BSLOL friends in attendance this year. See you all soon.