The eight Staten Island Ferry boats that carry 60 million people every year are ill-designed, poorly maintained safety hazards, a ferry captain has revealed.

“I don’t understand how the Coast Guard allows these boats to go out sometimes,” the skipper told The Post in an interview. “They really do put people at risk.

“If this were a private company, the Coast Guard would be all over them.”

The captain — who requested anonymity because he fears being fired for going public over safety concerns — said the ferries are plagued by poorly performing batteries, or phase cells.

They often fail, resulting in the shutdown of one or more of the four “drives” that are linked to propellers, making it at times impossible to slow, or even stop, the boat.

“Captains are concerned a big one is coming because of how unreliable the boats are,” he said.

In the past 11 years, there have been at least eight ferry mishaps, including six linked to mechanical failures and five in which the massive vessels rammed into piers while docking.

One such “hard landing” came on May 8, 2010, when the ferryboat Andrew J. Barberi smashed into the St. George Terminal on Staten Island with 244 passengers aboard.

Federal investigators found the 6,000-seat boat’s propellers failed following an electrical malfunction. The crash injured 50 passengers — three of them seriously — and caused $182,000 in damage to the terminal.

A year earlier, the ferryboat John J. Marchi sailed at full speed into a pier at the St. George Terminal, injuring 15. Electrical problems were again to blame.

“A transformer blew. It took down the one drive, and the other three drives went into standby mode,” the captain said of the July 1, 2009, smash. “They were pretty close to the dock, so when [the captain] tried to slow down, he didn’t have anything.”

The safety issues persist despite wholesale systemic changes adopted by the city Department of Transportation after one of the worst disasters in city maritime history — the Oct. 15, 2003, ferry crash that killed 11 passengers and injured 165 others.

Operating in fair weather and without mechanical issues, the Barberi barreled full speed into a concrete maintenance pier at the St. George Terminal. The pier cut through the 310-foot, 3,335-ton vessel’s steel skin like a knife, breaking beams, columns and seats — and severing human limbs.

Asst. Capt. Richard Smith had passed out alone at the helm after taking painkillers, while supervising Capt. Michael Gansas was nowhere near the wheelhouse. Smith fled the bloodbath and returned to his New Jersey home, where he locked himself in a bathroom, slit his wrists and shot himself twice in the chest with a pellet gun. He lived.

Smith, Gansas, ferry director Patrick Ryan and Port Capt. John Mauldin were criminally charged. Smith and Ryan were convicted of manslaughter and imprisoned. Mauldin received probation. Gansas’ charges were dropped, but he was fired.

The crash investigations rocked the insular world of municipal seafarers, where nepotism and lackluster staff performance were not just tolerated but the rule and whistleblowers were dealt with internally — sometimes with two-by-fours across arms and legs.

Following the Barberi tragedy — and $87 million in negligence settlements paid by the city — 72 staffers were fired or resigned, 118 were hired, rules were modified, outside overseers were appointed and the DOT promised a safer, more professional system.

But the boats are barely seaworthy, said the captain speaking with The Post in the first interview with a Staten Island Ferry pilot in recent memory.

Ironically, the most dangerous boats in the fleet are the newest ones — the three so-called Molinari-class vessels, which were christened in 2005 and cost taxpayers $140 million total, the captain said.

The John F. Kennedy, the oldest boat in the fleet, commissioned in 1965, is considered the most dependable, he said.

Each of the newest boats — the Guy V. Molinari, the John J. Marchi and the Spirit of America — are prone to breakdowns, he said, usually involving the four drives, two on each end.

“These [phase cells] tend to fail, and when they fail, it shuts down a drive,” the skipper said. “If you lose a drive, power is reduced, so if you go to slow down, you don’t know if it’s going to slow down or if it’s just going to take longer. We’re supposed to get the same response every time, but you don’t know.”

A balky drive doesn’t pose a major concern when a ferry is in the middle of New York Harbor and its captain has time to reset the system, he explained. But when the boat is docking and the pilot has only seconds to react, lives are endangered.

“You do a gradual slowdown anyway, but if you’re coming up on the dock and you lose a drive, it changes the situation,” the captain said.

Other aspects of the electrical systems are also problematic, the captain said.

A blown transformer on the Spirit of America shut that vessel down last year, he said, and now the boat is being retrofitted with electrical components in a trial that’s expected to eventually include the other two newer boats.

“They know these boats are s- -tty,” he said. “The bosses are trying to do the best they can, and there are limitations.”

The DOT defended its ferryboats, noting all have been certified for operation by the Coast Guard.

The Coast Guard last week refused to comment on the skipper’s allegations and said it could not immediately provide inspection data.

“While the Molinari class is fitted with four drives on each vessel, they can safely operate on one drive,” said DOT spokeswoman Nicole Garcia. “DOT initiated a project to upgrade the drives some time ago, and that project is well underway. The Spirit of America was the first vessel to be retrofitted. The other two vessels will be similarly retrofitted during this upcoming year.”

The captain pointed out that higher-ups have been fully aware of the boats’ day-to-day mechanical issues for years, but weigh that against not getting commuters to work on time.

“Nobody wants to be responsible for injuries or death,” the captain said. “The goal is to get people there safe.”

The ferries cost the DOT more than $108 million annually to run. The 20-minute ride each way is free to passengers.

For now, deckhands and captains will continue to make do with limited resources while under pressure from management to take boats out when they’re not in good shape.

“You’re responsible in one trip for more passengers than an airline pilot takes in a week,” the skipper said. “An average trip for us is 1,000 people. When they make us run the boats when they’re not healthy, that is adding a degree of danger.”