In sunny conditions at Troon, Norman bogeyed six of the first 10 holes and was 6 over before he finally birdied the par-4 13th. He birdied the final hole with a pitch to 3 feet.
The Australian said windy conditions, similar to the British Open, had an impact on his game.
I got to the first tee and I never played this golf course in this wind before, Norman said. I didnt feel that confident with some of the tee shots.
The 53-year-old Norman led the British Open at Royal Birkdale with nine holes to play Sunday and appeared on course to become the oldest winner of a major before he finished third behind Padraig Harrington.
While Norman struggled, playing partner Tom Watson made every green and missed only one fairway in a bogey-free 70. Andy Bean, John Cook, Kirk Hanefield and Nick Job were one shot off the leaders.
Vaughan made eight birdies for a 3-under 68 on the links course. But his round was hampered by a double-bogey and a triple. He recovered from the 7s on the sixth and 12th holes to play the last six at 3-under par.
It was either feast or famine, Vaughan said. Outside of those two hockey sticks (7s), it was a good round.
Romero had only one bogey, driving into a fairway bunker at the par-5 sixth hole.
Romero captured his second Champions Tour tournament three weeks ago at the Dicks Sporting Goods Open at Endicott, N.Y. He lost a playoff to Loren Roberts at the Senior British championship two years ago at Turnberry.
I feel strong, I feel good and I feel happy, said the Argentine, whose highlight was a 15-foot birdie putt at the 17th. I think this is my week. I love this tournament and I am in good form, especially my putting.
Watson was pleased with his round.
I dont think I have made all 18 greens ever in my life, said Watson, a three-time Senior British Open winner. I am very happy. I shot a good round of golf in unusual conditions with the wind changing direction.
Craig Stadler hit a hole-in-one at the postage stamp eighth hole ' the shortest in the history of the British Open ' winning 123 bottles of wine, one for every yard, as a prize from a sponsor.
Stadler used a pitching wedge to the front of the green and the ball bounced twice before rolling in. The ace happened after he birdied the seventh. Stadler finished with a 74.