When Tom McGuire boarded the 6:34 a.m. LIRR train in Merrick yesterday, he expected to arrive at Penn Station at 7:14 a.m. in time for work.

Instead, because of an Amtrak third-rail power failure near the Manhattan rail hub, his train got stuck in an East River Tunnel and had to be towed backward at 10 a.m. Then his train was rerouted to Hunterspoint Avenue in Queens, where he took the No. 7 train to his midtown office.

He arrived at work about 11 a.m. “You just have to take it in stride . . . I think we all have become pretty numb to delays,” said McGuire, 40, of Merrick.

Unbowed by his abominable morning commute, McGuire said last night he would trust the railroad, but knows it could let him down again.

“It looks like the railroad’s on time, and they fixed the issue . . . and hopefully there are no [other] issues,” he said.

The railroad reported only scattered delays Tuesday evening.

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The resilience of McGuire could come in handy heading into the summer repairs Amtrak plans at Penn Station.

McGuire has doubts about how the Penn project will impact LIRR commuters.

“From what’s coming out right now, it looks like the LIRR won’t be affected, which I really don’t believe,” he said.

The LIRR, despite recent problems, mostly blamed on Amtrak, still strikes McGuire as a better option than driving to Citi Field in Queens and taking the 7 train. The bank employee can’t telecommute because his responsibilities include in-person meetings with clients.

When complete, the East Side Access project linking the LIRR to Grand Central would smooth his commute. The long-delayed project is now expected to be finished by 2022.

“I’d love that,” said McGuire, adding, “I’m very skeptical they’re going to complete that project anytime soon.”

With William Murphy