After the calm conditions of Thursday when Rory McIlroy made the early running with a six-under 66, the Royal Liverpool course was far less benevolent as the players returned to action with a warm wind blowing off the Dee Estuary.
By late morning, only five players had broken par on the outward nine but birthday boy Coetzee showed what could be done on the homeward stretch with four birdies in six holes after the turn to briefly join McIlroy at the top of the leaderboard.
"I think the wind actually helped me a little bit really because of the way I shape the ball I could commit to it," said Coetzee, who challenged strongly at Sandwich three years ago when he finished in a tie for 15th.
His share of the lead did not last long, however, as the Pretoria native dribbled a par putt past the hole at the par-five 16th and then got in a tangle at the 17th after finding deep rough and leaked another shot to drop back into the pack.
McIlroy was due to begin his second round at 2.27pm when forecasters predict the winds will ease.
Three-times champion Tiger Woods, who ground out a first-round 69, was teeing off a few groups ahead of McIlroy.
Several big names trying to kick start their challenges early on Friday suffered frustration on the par-72 layout.
World number one Adam Scott, who began the day two shots off the lead, dropped shots at the second and third holes, both par fours into the wind, although he did earn one back at the fifth.
Defending champion Phil Mickelson, who fell in love with links golf last year when he triumphed in Muirfield after 19 failed Open attempts, eagled the fifth, but also dropped shots as he stayed one stroke over par heading for the turn.
The American drove out of bounds at the par-five 10th but still managed a par with his second ball.
U.S. Open champion Martin Kaymer had a mixed bag on the outward nine, beginning his second round with two birdies but then dropping four shots in three holes from the seventh.
Masters champion Bubba Watson clawed back some of the damage from an opening round 76, picking up three birdies in his opening 10 holes on Friday.
Celebrating his 28th birthday in style, Coetzee's early move began with a birdie at the fifth but it was his three birdies in a row from the 13th that rocketed him into contention.
He drained a 50-foot putt at the 13th, then watched another long one disappear at the next before a pinpoint tee-shot at the short 15th completed a 2-3-2 contribution to his scorecard.
After dropping a couple of shots, Coetzee then steadied the ship, knocking in an eight-foot birdie putt on the last to comfortably take the clubhouse lead.
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- Rory McIlroy