Spokesmen for the Coast Guard and the American Bureau of Shipping conceded yesterday that their safety inspectors missed obvious and critical flaws in the hatch covers on the cargo ship Marine Electric when they certified it fit for sea a year before it sank off the Virginia coast.

Testifying before a congressional subcommittee, Rear Adm. Clyde T. Lusk, chief of the Coast Guard's Office of Merchant Marine Safety, said one of his inspectors had done a "less than perfect job" in failing to spot hatch covers rusted to paper thinness and so warped by age they would scarcely close.

"It certainly does appear he could have been a lot more attentive, . . . " Lusk said.

The admiral and other witnesses drew a portrait of a U.S. merchant marine policed by a Coast Guard undermanned, underfunded and in many cases undertrained to prevent such casualties as the sinking of the collier Feb. 12 off Chincoteague, Va., with a loss of 31 lives.

Equally at fault, they indicated, were crewmen who failed to protest unsafe conditions, shipowners who failed to correct them and shipping bureau surveyors who pronounced the ship seaworthy though its hatch covers were missing at the time.

"Would it be fair to conclude," asked Chairman Gerry E. Studds (D-Mass.), "that at least in respect to this ship, at least in respect to these hatch covers the American Bureau of Shipping did not do the job expected of it by the Coast Guard and by the public?"

"From the information you've given me," said shipping bureau vice president John Borum, "that would be a fair conclusion." The bureau is an industry group that conducts annual dry-dock inspections of all American ships and certifies them seaworthy for the Coast Guard. Survivors said stormy seas poured through the Marine Electric's leaking hatch covers causing the ship to "sink by the head."

Studds' subcommittee is considering legislation to tighten inspection requirements and stiffen penalties for U.S. flag vessels like the Marine Electric, a 38-year-old World War II tanker that had been "jumboized" into a 605-foot coal carrier twice its size.

Several witnesses indicated yesterday that enforcement of existing regulations is a greater need than new ones.

Eugene Kelly, former third mate of the Marine Electric and one of the three crewmen to survive its sinking, said "there are no braver men" than the coast guardsmen who rescued him from the gale-whipped Atlantic, but said Coast Guard ship inspectors are rarely equipped for their "grave responsibility."

"I've seen young people come on board. . . with no idea what they're supposed to look for," Kelly said. "Some of their inspections last less than 15 minutes."

The Marine Electric's last Coast Guard inspection, he said, was just such a brief affair, confined making sure the proper books and charts were on the bridge.

"Books and charts," Kelly said, "won't keep a ship afloat."

Although most witnesses attributed the loss of the Marine Electric to the age of the ship and its hatch-covers, no official determination of the cause of the wreck has been made. Coast Guard hearings on the subject resume Monday in Portsmouth, Va.

Capt. Henry A. Downing, executive vice president of Marine Transport Lines Inc. of New York, which owned the vessel, blamed the loss of the vessel on a missing six-ton anchor, which he said must have come loose and battered the hull as the ship made her way from Norfolk to Somerset, Mass., with 24,000 tons of coal.

He sought to minimize importance of the hatch covers, saying the ship had "no major deficiencies which made it unfit for sea."

Had she not sunk, he said, the Marine Electric would probably have been operated for another three years or more, leaky hatch covers or not. "You do get a lot of wastage. . . a lot of holes," in old ships, he said, but they are seldom so serious they cause a ship to be removed from service. That, Downing said, "would be a financial decision."