John Duddy landed a sledgehammer right hook that finished off Shelby Pudwill at 1:31 of the first round in the main event of last night’s “Irish Express” boxing card at the Theater at Madison Square Garden.

Duddy, a native of Ireland, was hit only four times in front of a sold-out crowd that seranaded him to victory, chanting his name and bursting into song as he improved his record to 16-0.

Last night’s knockout, the 14th of his career, earned Duddy the WBO Continental Americas middleweight championship.

Pudwill (21-3-1, nine KOs) never had a chance as Duddy came out firing with the largely Irish, flag-waving crowd starting their St. Patrick’s Day celebration a little early.

The 26-year old Duddy, a product of Irish Ropes Boxing Club in Rockaway Beach, knocked Pudwill to the carpet two times in the match’s first 1:30. He needed only the one heavy right to finish it, coming out of the second stoppage, to capture the title. “Nobody expects these fights to be so short,” Duddy said. “He’s a great fighter.”

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On the undercard:

Brooklyn welterweight Martin Davis, with a heavy left-handed flurry, won his professional debut with a first-round TKO against Joseph Davis, who landed only seven punches.

Local favorite Peter “Kid Chocolate” Quillin (3-0) turned Willie Cruz into pudding with a second-round TKO in a super-middleweight clash and celebrated by tossing candy to the crowd.

Super-middleweight Joe Greene took a sixth-round decision from Brian Norman.

Ireland’s Maureen Shea improved to 5-0 with a four-round decision over LeAnne Vilarreal in women’s junior lightweight.

James Moore (4-0) dispatched Joe Felix by TKO 26 seconds into the third round.