MELBOURNE, November 17, 2013 (AFP) - US Masters champion Scott began the day five shots clear of Kuchar, but could not maintain his sub-par form of the previous three rounds and fell two shots behind the American world number eight with four holes to play.
But the Australian held his nerve on the closing holes and picked up a birdie on the par-5 15th, while Kuchar, two playing groups ahead, bogeyed the 16th then double-bogeyed the last to lose his winning chance.
Scott enjoyed a two-shot buffer entering his last two holes and parred both to finish with an even par 71 to be 14-under 270 for the tournament with Kuchar (68) two shots back and Fiji's Vijay Singh (71) third at 10-under.
The victory keeps alive Scott's hopes of claiming the Australian triple crown after winning last week's Australian PGA on the Gold Coast and with the Australian Open to come at Royal Sydney in two weeks.
Before then Scott will again take on Kuchar, Singh and others at Royal Melbourne this week when he partners Jason Day for Australia in the World Cup.
"I've never won back to back weeks so this is a first and something that I like," Scott said.
"I think it's very hard to win two tournaments full stop, let alone back to back, so I'm quite pleased with myself this week."
"Sometimes you win a little bit ugly. All the good stuff I had done in the first three rounds counted for a lot, even though it wasn't the prettiest golf today."
While disappointed with his finish, Kuchar said he was well placed to once again take on Scott at the World Cup.
"At Royal Melbourne you can really pay the price for being just a little off when you are playing aggressive and it got me at a bad time," Kuchar said of his double bogey finish.
"It was a rough way to end but it's the nature of the game, you have to be ready to bounce back.
"The guys who look toward the positive seem to do well in the long run. You see guys some carry over some bad momentum but I know better than that."
Scott started the day with a four-shot lead over Singh and three others and five clear of Kuchar, but he struck trouble on the par 3 fifth, when he went from one bunker to another and did well to escape with bogey.
Scott birdied the sixth, but dropped another shot on the seventh.
By the time he completed the front nine in even par Kuchar had reached five-under for the day and joined Scott on 14-under.
Kuchar, who bogeyed the second, had made six birdies in nine holes from the third to the 11th.
Scott edged back in front with a birdie on the 11th but he struck further trouble on the par 3 14th, when his tee shot found a bad lie in a greenside bunker.
His second shot rolled into light rough on the opposite fringe and after chipping to less than three metres, he never looked like making the putt and took a double-bogey.
That left Scott 13-under, one behind Kuchar, who soon increased his lead with a birdie on the par 5 15th.
Scott birdied the same hole to cut the gap to one, before Kuchar bogeyed the 16th to rejoin Scott on 14-under.
But Kuchar was unlucky on the 18th, finding the wall of a greenside bunker with his second shot and he could only jab his third shot onto the floor of the trap, on his way to double bogey.
That left Scott with a two-shot cushion with two to play and he parred both to complete victory.
Leading scores after the final round of the Australian Masters at Royal Melbourne (par-71) on Sunday (Australia unless stated):
270 - Adam Scott 67-66-66-71
272 - Matt Kuchar (USA) 71-66-67-68
274 - Vijay Singh (FIJ) 72-68-63-71
275 - Nick Cullen 65-69-69-72
278 - Ryan Fox (NZL) 68-71-66-73, Matthew Griffin 69-65-69-75
279 - Marc Leishman 71-71-72-65, Aron Price 73-71-67-68, Jason Scrivener 69-71-70-69, Geoff Ogilvy 71-72-67-69, Mathew Goggin 72-71-67-69, Brendon De Jonge (ZIM) 68-70-68-73
280 - Matthew Millar 69-70-71-70, Gaganjeet Bhullar (IND) 69-72-69-70
281 - Nathan Holman 68-65-70-78
282 - Gareth Paddison (NZL) 74-69-72-67, Peter Senior 74-68-71-69, Michael Hendry (NZL) 72-69-71-70, Maximilian Kieffer (GER) 67-72-72-71
Selected scores:
284 - Jin Jeong (KOR) 73-70-71-70
288 - Pan Cheng-tsung (TPE) 70-73-71-74