He finished with the day's best round of 4-under 68 to post a 36-hole total of 7-under-par 137 in windy conditions on the North Shore of Oahu.
Hubert Green shot 2-under 70 for a share 5-under 139 with first-round co-leader John Jacobs, who followed his opening 68 with a 71. Don Pooley, making only his fifth Senior Tour start after turning 50 in late August, carded a 71 to finish alone in fourth place at minus-four.
Irwin, one stroke off the lead at the start of the day, carded back-to-back birdies when he followed a 25-foot putt at the sixth hole with a 10-footer at the seventh. He reeled off six straight pars, including saves from six and eight feet, before surrounding a bogey at the 15th with birdies at Nos. 14 and 16.
Irwin closed with a two-putt birdie from 40 feet at the 539-yard, par-five 18th.
Irwin, who is looking to extend his lead on the all-time Senior Tour win list, said his play has been affected by the 15 to 30 mile per hour winds that have whipped the Turtle Bay Resort's Palmer Course the first two days.
'Hardest thing for me today was committing to the shot,' the 56-year-old Irwin noted. 'It's been a while since we've played in this kind of gusting wind.'
The scoring average for the field rose from 73.538 in round one to 74.130 on Saturday. The number of sub-70 scores dropped to just three after nine were recorded on Friday.
Irwin has won three Senior Tour titles -- as well as two unofficial Senior Skins Games -- in Hawaii. The most recent of his official Hawaiian wins came at the 2000 Kaanapali Classic in Maui, the event that was replaced on the 2001 schedule by the Turtle Bay Championship.
Irwin, who tied Lee Trevino for first in Senior Tour victories with 29 after his Kaanapali Classic triumph late last season, took over the top spot with a win at the inaugural Siebel Classic in March. He then moved two ahead of Trevino with his 31st career victory on the elder circuit, at Bruno's Memorial Classic in April.
So far this year Irwin has won two of the four tournaments in which he has taken at least a share of the lead into the final round.
Dick Mast held the lead at 6-under after birdieing three of the last four holes of his front nine. He suffered four bogeys on the back side, however, to finish tied for fifth place with an even-par 72.
George Archer was only one stroke behind Irwin through 17 holes Saturday but double-bogeyed the 18th to join Mast at 3-under 141. Archer also shot 72.
Among seven players knotted at two-under was Allen Doyle, who currently tops the season money list with $2,332,942. Doyle made the biggest move in round two, firing a 3-under 69 to vault from a tie for 34th into a tie for seventh place.
Click Here for Full-Field Scores from the Turtle Bay Championship.