An American journalist claims to have uncovered evidence that Oracle Team USA broke the rules in their famous comeback win over Team New Zealand in the 2013 America's Cup.

Oracle's incredible 9-8 win in the San Francisco regatta after trailing Emirates Team New Zealand 8-1 is widely regarded as the greatest comeback of all time. But former Wall Street Journal reporter G. Bruce Knecht has cast doubt on Oracle's methods.

In his newly released book, The Comeback, Knecht reveals Oracle used a sailing technique that was prohibited under the rules.

Knecht claims Oracle used a technique known as "pumping", whereby the crew reeled in the wing to the optimum position, then let it out again. This was done repeated and as rapidly as possible.


Given the pressure of the wind against the enormous 40m wingsail, the technique was hugely effective with the back-and-forth movements providing added propulsion.

But pumping was prohibited under the rules. Propulsion is only supposed to come from the boat's normal interaction with the wind and water - not man-made energy. The crew can adjust the trim of the wing, sails, rudders, daggerboards and hulls, and perform other acts of seamanship, but pumping of the sails is prohibited.

The book acknowledges the questionable technique is not the only reason Oracle won, outlining "a perilous re-engineering of the boat", a crucial crew change and the "superhuman" efforts of the crew and management when faced with an seemingly insurmountable deficit.

"Oracle's reincarnation was born," Knect writes, "of not just never-say-die determination and unspoken prohibitions on finger pointing and naysaying, but also of an almost reckless willingness to accept risk."

Team New Zealand were not prepared to comment on the book's findings. A spokesman for the syndicate said he was yet to read the book, and the team are "looking ahead rather than backwards".