A...Duck?

To complete their 30,000-mile quest through Central and South America, the Operation Americas crew needed a robust vehicle. Thus, they invested in their beloved "Duck" (or DUKW). An undated press release from reporter Spencer Ketchum at the J. Walter Thompson Company provides a detailed description of the Duck in detail:

It was purchased in June, 1961 in Akron, Ohio, for $1,700. About $4,000 additional was spent in fixing it up and getting tires, Bob Hinds, the leader of the expedition estimates.

The vehicle is late-World War II surplus. In Army jargon it is known as: “truck, 2 ½ ton, 6x6, Amphibian, GMC model DUKW-353.”...Its overall length is 31 feet—plus another several feet for an outrigger to hold two, Johnson V-75 outboard engines. Width is eight feet. Its welded steel hull plus engines and equipment weighs a hefty ten tons. Its payload (continuously exceeded) is 5,000 pounds.

Regular power for the duck is supplied by an [sic.] 135 horsepower, six cylinder, value-in-head truck engine. Power is supplied to all three axles, if necessary, as well as to a propeller drive shaft for on-the-water travel.

The lads thought that the single propeller might not have enough muscle when the going got rough (which turned out to be true). They thought that auxiliary power, such as outboards, would be the answer; and it was [sic.].

...Separate fuel tanks were provided to provide the necessary gas-oil fuel for the V-75 outboards supplementing the 140 gasoline capacity of the duck’s main fuel tank for its own motor.

The release also describes the Duck's Johnson Motors:

The Johnson Motors people equipped the duck with two 75 horsepower outboard engines on a special transom with separate controls for operations by water because the boys found the duck’s own power plant of a single 135 horsepower engine insufficient for the loads and driving conditions to be encountered.

Additionally, according to a USIS press release from March 28, 1962, the Duck "drinks" gasoline, of which it can hold about 150 gallons, "like a thirsty desert camel." 

Famously, the crew named their DUKW-353 "El Pato Valiente" (The Brave Duck)—although, at times, they simply called it "the Duck." To add character to the vehicle, a volunteer artist painted Donald Duck on either side of "El Pato Valiente."