Hunter Mahan birdied the final three holes Friday for an 8-under 64 and a two-stroke lead after the second round of the Canadian Open.
Coming off a ninth-place tie last week in the British Open, the five-time PGA Tour winner had eight birdies in his bogey-free round at Glen Abbey to reach 13-under 131.
John Merrick was second after a 62. He tied the course record set by Leonard Thompson in 1981 and matched by Andy Bean in 1983 and Greg Norman in 1986.
Bubba Watson was 9 under after a 67. Aaron Baddeley and Patrick Reed shot 68 to reach 8 under.