The quadruple bogey was only one short of the record high score at the hole in Masters history.
And although the US Open and US PGA champion hit back with five birdies his round of 73 for a one-under total left him too far back to challenge today. He said: "Obviously my chances went then. These things happen in the game and you can't do much about it."
Harrington's trouble began when he pulled his drive on the par-five hole into the trees.
His second shot hit a branch and rebounded into more trouble. A penalty drop followed and his next went into a ditch. He hacked out, came up short with his sixth and then failed to get up and down.
Leading Europeans are Britain's Ian Poulter and Lee Westwood, round in 68 and 70 respectively to be joint 10th.
Alongside Harrington on one under were Justin Rose (71) and 51-year-old Sandy Lyle (73), while Luke Donald's 72 left him one further back.
Rory McIlroy - still in the tournament after being cleared of any wrong-doing in a bunker on the final hole of his second round - added a 71 to start the final round on level par.
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