“The conditions were so good for us this morning,” said McIlroy. “It felt like if you didn’t play that first nine in three or four under, you were losing strokes to the field.
“I did a lot of good things today, a couple of loose shots here and there but overall it was a good day. I’m excited for the weekend, right in contention.”
England’s Matt Fitzpatrick, who has been battling form struggles for much of the year, ignited his title hopes with a 63 to move eight under alongside Marco Penge.
Fellow countryman Harry Hill was two off the clubhouse lead after posting 64.
US Open champion JJ Spaun is set to miss the cut after three bogeys in a 72 that left the American two over.
Defending champion Robert MacIntyre, world number Scottie Scheffler and overnight co-leader Sepp Straka were among the later starts on Friday.
Gotterup was threatening to break 60 after covering his ninth birdie of the day on 14, but four pars followed.
“It [59] never really crossed my mind,” said the 25-year-old.
“I made the putt on 14 and I was like, all right, I’ve got 16 and obviously 17 and 18 are pretty tough. So I really wanted to get 16.
“I’m not going to complain too much when I make my birdies on a course that isn’t always typically easy.”
