The U.S. Parole Commission yesterday cut one year from the three-year prison sentence of former Maryland Gov. Marvin Mandel, overriding hearing examiners who recommended that Mandel serve his full term.

Mandel, who entered the federal prison camp at Eglin Air Force Base last May, now is expected to be released on May 14, 1982. The commission gave no explanation for why it overruled its own hearing examiners.

The ruling followed a last-minute lobbying effort by Mandel's wife and supporters and friends who contacted the White House and the officers of Sen. Charles McC. Mathias (R-Md.) and Baltimore Mayor William Donald Schaefer for help in securing the Parole.

The quest for high-level influence apparently got nowhere. Ocean City Mayor Harry Kelley, who said he contacted White House aides on Mandel's behalf, said: "They wouldn't touch it with a 10-foot pole."

"Normally, when we do get a request of this kind, we simply ask the parole board what the status of the case is and when it comes before the board," an aide to Mathias said.

The commission also cut the terms of two of Mandel's condefendants and close friends, W. Dale Hess and Harry w. Rogers III. Hess' sentence was cut by 16 months and Rodgers' was cut one year.

Action on the parole request of codefendant Irvin Kovens was postponed because Kovens is awaiting surgery after suffering a heart attack while at Eglin last month.

All four men applied for parole in mid-June. As first offenders, they technically were eligible for parole as soon as they went to prison.

The request was bucked from a regional parole commissioner in Atlanta, who ruled in August that the case had drawn too much national attention to be decided by his lone vote, to the national commission in Washington.

The national commission then sent the case back to Atlanta, along with some new material from the U.S. attorney's office in Baltimore, for further consideration.

Hearing examiners presented the information to Mandel in September and then recommended that he should serve his term "to the expiration," informed sources said, calling the recommendation unusual for its severity.

The case then moved back to Washington, where three national commissioners yesterday added their votes to that of the Atlanta regional commisioner. The commission does not reveal vote counts.

The lobby effort to secure Mandel's release in spite of the hearing examiners' recommendation apparently peaked on Tuesday, the day before Mandel's case came before the commission.

On that day, Mathias' Baltimore office received 20-25 calls supporting the ex-governor's early release, according to Dan Zaccagnini, an aide.

Jeanne Mandel also called, Zaccagnini said.

"The tone of all the calls was that yes, he has been convicted, but enough is enough," said Zaccagnini. "Mrs. Mandel put a little more emphasis on the same message."

Mathias treated the requests as if they had come on behalf of any other constituent, another aide said.

"Normally when we do get a request of this kind, we simply ask the parole board what the status of the case is and when it comes before the board," the aide said.

Baltimore Mayor Schaefer, who grew up politically with Mandel, could not be reached for comment on his response to the calls that came into his office.

Mandel and his three codefendants can appeal yesterday's ruling to the full, nine-member national commission, a Justice Department spokesman said.

The scheduled release dates set yesterday are contingent on good behavior. Mandel could have been released in September 1982 in any case because of accumulated good-conduct time.

Mandel and five codefendants were convicted in August 1977 on mail fraud and a racketeering charges arising from a scheme in which Mandel received more than $350,000 in gifts in exchange for helping his friends increase the value of their stock in the Marlboro racetrack.

The presiding judge at his trial originally gave him a four-year sentence, but later reduced it to three.

In a brief statement released along with its decision, the parole commission explained its reason for setting different release dates for Mandel, Rodgers and Hess.

Mandel, they said, used his position as governor to further the political corruption scheme and caused "a significant breach of public trust." However, they added, he earned less than his codefendants from the scheme.

Rodgers, who received the same treatment as Mondel, was a "primary benefactor of the scheme," the commissioners said.

Hess, whose sentence was cut four months more than that of Mandel and Rodgers, was also a primary benefactor but did cooperate with state officials in procecuting other cases, according to the statement.

Hess is scheduled to testify as a government witnes against Harford county executive Thomas Barranger, who is now on trial on political corruption charges. Hess has been serving his term at the prison camp at Maxwell Air Force Base in Montgomery, Ala.

Of the other two codefendants, William A. Rogers, Harry's brother, was sentenced to one year of public service work in Baltimore while Ernest N. Cory Jr., an attorney who was disbarred, was given suspended sentence.