From there, however, Kuchar had a birdie chance on the final 13 holes he made.
The victor of the Mayakoba Classic in Mexico in November, world No.32 Kuchar briefly surrendered the lead to Putnam after three bogeys in his first five holes on Sunday. "I didn't find myself in any trouble".
Keith Mitchell had a 63 to pull within four shots, along with Chez Reavie, who fell back with three straight bogeys early on the back nine.
"I anticipate needing another good score tomorrow, " Kuchar said.
The 40-year-old four-time Ryder Cup team member - who won a bronze medal for the United States at the 2016 Rio Olympics - won for the second time in the 2018-19 season after his victory in the Mayakoba Classic in November.
Kuchar's final-round 66 put him at 22-under 258 for the tournament, with Putnam finishing at 18 under with a 2-under 68 on Sunday. It was nice to have that pressure and be able to come through and make some birdies coming.
"It was awfully steady and bogey free".
The only other time Kuchar won twice in the same season was in 2013, when he won the Match Play Championship in Arizona in February and the Memorial in early June.
Kuchar ran off four birdies in five holes to start his second round on Friday, handled the par 5s at Waialae again and finished with another round 63.
He never looks to be under stress, though Kuchar says looks can be deceiving.
For Kuchar, the victory will probably propel him all the way to the Tour Championship later this season and could even be the start of a career year.
After shooting 67 on Thursday, Leishman fired a six-under-par 64 (131) on Saturday (AEST) to be alongside American Ted Potter, five strokes behind Matt Kuchar, who dazzled with back-to-back 63s for a 14-under-par two-round total of 126.
Peter Jung, who qualified by winning an amateur tournament, played in his first PGA Tour event. He joins Xander Schauffle in the two-win club for this season and now has almost eight months to notch the first three-win season of his long, consistent and successful career.
The Sony Open is more about work than play, and he's having just as much fun.
He returns in two weeks at Torrey Pines.
It was a further stroke back to Davis Love, who finished solo seventh with a 65 for 264. Reavie made more eagles - three - than birdies, of which he had only one.
"Didn't feel as easy as the first two days", Putnam said.
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