Londonderry’s Lauren Doherty battles Merrimack’s Gillian Waller for the ball during Londonderry’s 1-0 win in overtime in Division I field hockey at Merrimack High School on Wednesday.

MERRIMACK — The Londonderry field hockey team huffed and puffed but couldn’t find a way to blow the Merrimack house down in 60 minutes.

Eventually, senior Courtney Shay did it herself, firing a rocket of a shot into the goal 7:35 into overtime to give the Lancers a 1-0 win and improve their record to 3-0 on the young season.

“For her to finish, I’m not surprised,” Londonderry coach Nichole Treadway said. “For her to step up and do shows her character. She’s going to go in and do the job no matter what.”

The end came midway through overtime when Shay sprinted down the right side, took a pass and unloaded a full slap shot from a tight angle.

The goal capped a game that was dominated by the Lancers from start to finish. The first half was more even but tilted in favor of the Lancers, and Londonderry picked it up with a vengeance in the final 30 minutes.

The Lancers outshot Merrimack 17-2 and held the Tomahawks without a shot on goal in the second half or overtime.

“We just think keep going,” Shay said. “They’re going to fall eventually. Just keep hitting on net. Anyone can hit it in.”

The Tomahawks (0-2) kept the game scoreless thanks to a combination of timely defense, poor ball movement from Londonderry and Heather Rohr.

Rohr was dominant in net, notching 16 saves and playing with a controlled intensity all game.

“She was amazing,” Merrimack coach Ann MacLean said. “It was all sorts of saves. She did a great job. I was so pleased. Last year we lost five starting defense so these are all new players, and Heather was amazing.”

The Lancers drew 14 penalty corners but couldn’t turn them into many quality scoring chances. Balls would bounce over sticks or a Tomahawk would clog a passing lane before a play developed.

Londonderry’s deep roster played a big role in the victory, but it made the missed chances no less frustrating.

“Our theme has been to write our own script and I don’t think we did that in the first two halves,” Treadway said. “I think we were slow to the ball, slow to the move. I think mentally I don’t feel like we were mentally there. So going into overtime that’s what we talked about needing to do.”

Londonderry hosts Timberlane and Merrimack goes to Winnacunnet on Wednesday.