Irwin, who held a seven-stroke lead entering the final round of the second major tournament of the year, fired a 68 on to finish at a 14-under 274, 12 shots better than Dale Douglass and the 1991 champion, Jack Nicklaus.
John Morgan, Jack Kiefer and Gibby Gilbert finished tied for fourth at one-under. Kiefer shot a 70, Gilbert fired a 71, and Morgan a second straight 72.
Irwin, 51, twice the US Open champion, picked up his third victory of the year and his seventh career Senior Tour title and overtook Gil Morgan and David Graham at the top of the money list with $596,531.
The previous-best victory margin at a Senior event was 11 strokes, shared by Arnold Palmer at the 1985 Senior Tournament Players' Championship and Orville Moody at the 1988 Vintage Chrysler Invitational.
Irwin started his round by eagling the par-five, 539-yard third hole, hitting a four-wood to the green before sinking a 35-foot putt. Irwin followed that with a birdie on the fourth.
After making the turn, Irwin hit a sand wedge on 10 before tapping in for birdie. His only blemish was on 11, where he three-putted for bogey. He also sank a 12-foot birdie putt on 16 before parring the final two holes. ''My hope was to continue playing the type of game I had been playing, and that was to be aggressive when I felt the need or the situation arose," Irwin said.Reuse content