IL Mostro made a strong closing push Sunday afternoon to be first to finish in the 110th Mac. Il Mosto, a Volvo 70 owned by Peter and Chris Thornton of Burr Ridge, reached Mackinac Island at 6:11:22 p.m.

But for the second time in seven years, tragedy overshadowed racing in the Chicago Yacht Club Race to Mackinac. The Mac is the world’s oldest freshwater distance race, 333 statute miles from Chicago to Mackinac Island, Mich.

Forty minutes after the start Saturday, Jon Santarelli, 53 of Lincoln Park, went overboard on Imedi. Despite searches over nearly 47 square miles by 20 boats and three helicopters from fellow competitors, the Coast Guard, the Chicago Fire Department and Police Department, he was not found Saturday. The unsuccessful search resumed Sunday.

“My heart goes out to the family’’ Chris Thornton said. “You do this to have fun and nobody ever expects a tragedy.’’

Conditions were challenging with mostly upwind sailing into northerly winds and 6- to 8-foot waves. By 6 p.m. Sunday, a sixth of the fleet, 50 boats, had retired.

Il Mostro used those conditions to pass the leading cruisers, Albatross and Broderi, Sunday afternoon. The cruisers sailed a day earlier on Friday than the racing sections.

“For an upwind race, our lapsed time is pretty solid,’’ Chris Thornton said.

Their lapsed time of 28 hours, 11 minutes, 22 seconds corrected to 43:09:29 in handicapping. The Mac is a handicapped race, so rarely are the first to finish the race winners. But first to reach the island matters to the Thorntons. The Royono Trophy goes to the first monohull to finish.

“There was heavy air, 29 knots of north breeze all night and 6- to 8-foot waves,’’ Thornton said. “It was a challenge physically. But Il Mostro has done two around the world races.’’

The crew of Maggie Mae captured the duality of the challenging conditions with this tweet: 40 knots on Maggie Mae 262 Beneteau Waves 8ft No 10! Beats any ride at Disneyworld!”

Windquest crossed at 8:07:12, shortly after catching and passing Albatross (8:10:25) and Broderi (8:20).

A crescendo of boats finished Sunday evening. The bulk of the fleet should finish today in a relatively fast race, both helped and made challenging by the conditions.

As Tim and Nancy Snyder put it Saturday afternoon on their Cheap Thrill twitter, “40 miles up the course and everything inside the boat is wet. Crew on rail are alternating who sits in lead spot.’’

Conditions eased Sunday, compared to Saturday night.

As Endeavour’s Twitter put it earlier Sunday: “Passing sleeping bear. We see this thing called a “sun’’ we’ve heard rumors about.’’