He went from a shipwreck to a trainwreck.

Residents of a tony Jersey Shore town are furious after the shipwrecked Florida boater they welcomed with open arms turned out to be an ex-con with a rap sheet longer than a bluefin tuna.

Lawrence Kaehler, 51, was trying to sail solo from New York Harbor to Cocoa Beach, FL, but managed to make it only 48 miles. When rough weather caused him to lose control of his front sail, he frantically attempted to course correct and dock in what he believed to be an inlet — but he ended up running aground on the beach in Sea Girt.

“It got really, really nasty, really fast. It probably was four to six-foot waves, and probably about 25-mile-an-hour, 30-mile-an-hour winds,” said Kaehler, who owns a flooring business in Florida.

At first, locals rushed to help the castaway.

“I would hear people like genuinely concerned for my safety . . . And I’d just pop my head up [out of his boat] and be like, ‘No, I’m okay,’ ” he told The Post.

Good Samaritans offered him food and even a bed. A local company dug a trench to help him get the boat, named the Alestorm, back out to sea.

“We almost had it two times,” but more bad weather foiled the attempts, he said.

On Oct. 21, the state police issued a citation ordering him to remove the boat or face a potential $1,000 per day fine.

The tide of support began to turn as his boat languished — and revelations began to unfold.

Local internet sleuths soon discovered Kaehler’s checkered past, and police sources and public records confirmed at least eight past felony convictions, including for cocaine possession, dealing in stolen property and DUI.

“That past bothers me. Who knows what he had on the boat?” Sea Girt resident Matt Isabella said.

Shocked local resident Charles Newman said, “I can’t believe the town didn’t put it in a dumpster. I can’t believe it’s still intact on the beach.”

Kaehler said that he is trying to “move forward” from his unsavory past. He admitted he served nine months in prison and was on probation from 2017 to 2024.

“I think I’m a pretty decent dude, you know? I try to help people out and I don’t harm anyone else, just myself… drugs are bad,” Kaehler said.

The town twice offered to help him remove the boat, which has languished in the sand for seven weeks, but he refused because the town insisted he hold it “harmless” in case the vessel was damaged. Kaehler declined to share how much he paid for the Catalina, but said it was either an ’83 or ’85 model, which can sell online for $10,000-$25,000.

He attended a virtual court hearing Wednesday, where he pleaded not guilty to abandonment of a vessel, and told the State Attorney General he would work with the borough to remove the boat.

Additional reporting by Helayne Seidman