Carolan posted a 4-under 67 at the Keowe Vineyards course. Play was rotated over the two courses for the first two rounds but all action will be contested on the Cliffs Valley Course for the final two rounds.
Brian Hull carded a 7-under 65 at the Cliffs Valley course while Shane Bertsch, who shared the first-round lead with Carolan, shot a 3-under 68 at Keowe Vineyards. The pair are knotted in third place at 10-under-par 133.
Jack Nicklaus, who is making his second consecutive appearance in this event, shot a 1-under 71 at Cliffs Valley but will not be around on the weekend. He finished at 3-under-par 140 and missed the 36-hole cut by a stroke.
Nicklaus' long-time golf rival Gary Player also failed to make the cut. Player carded a 3-over 75 at the Cliffs course and posted a two-day total of 5-over-par 148.
Wetterich opened on the back nine and wasted little time in going into red figures. He tallied four birdies in a row from the 11th, including tap-in birdies at 12 and 13.
He bogeyed the 16th but reclaimed the lost stroke with a 20-foot birdie putt at the last.
Wetterich went on another birdie run on his second nine. He rattled off three in a row from the second and added a tap-in birdie at No. 6. Wetterich bogeyed the seventh but tapped in a 3-footer for birdie at the ninth to get a piece of the lead.
'I'm very excited about the round,' said Wetterich, who won last year's Louisiana Open. 'I haven't played this well in a long time. I'm just trying to be patient.'
Carolan played steady on Friday. He made his first birdie at the ninth when he two-putted from 35 feet. Carolan recorded back-to-back birdies at 13 and 14, then holed a 14-foot birdie putt at the par-3 16th to polish off his bogey-free round.
'I've been scoring terribly lately but hitting the ball well,' said Carolan. 'It's been frustrating. I keep thinking I'm a better player than I've been showing. I was thinking about winning on the first tee.'
Rick Price (65), Kyle Thompson (67) and Brad Bryant (68) share fifth place at 9-under-par 134. Jon Mills (65), Paul Gow (67), Jeff Klauk (65), Richard Johnson (66) and two-time Nationwide Tour winner this year Jimmy Walker (68) are tied for eighth at minus-8.