In some editions yesterday, a story on page A25 stated incorrect operating speeds for patrol boats used by Iran. Their maximum speed is 60 mph. (Published 7/27/87)

Iran has converted a Swedish patrol boat capable of speeds up to 60 mph into a deadly hit-and-run attack craft that Defense Department sources said is one of the three main threats to U.S.-reflagged Kuwaiti oil tankers plying the Persian Gulf.

The speedboats, made by Sweden's Boghammer Marin Co., have been armed with machine guns, hand-fired rockets and 106 mm recoilless cannon capable of piercing the hull of tankers and causing considerable damage, the sources said.

Iran's Revolutionary Guard, which is developing its own small navy independent of the Iranian military, has used the Boghammer speedboats in attacks that began in February on international shipping in the gulf.

Shipping sources said the Revolutionary Guard's tactics using the fast boats are markedly different from past attacks on tankers, in which Iranian helicopters or airplanes sought by radio or other means to identify a vessel's nationality and cargo before taking hostile action.

But the Revolutionary Guard speedboats approach vessels and without warning, begin firing -- sometimes for as long as 20 minutes -- and then speed away. Some of the attacks have occurred at night or in early morning.

Pentagon spokesman Robert B. Sims described the speedboats last week as one of the three major threats facing the U.S. warships and the reflagged Kuwaiti oil tankers they are escorting. The two others are Iran's mines and Chinese-made Silkworm missiles. A mine damaged a reflagged Kuwaiti tanker early Friday; Iran has not said that it planted the mine.

Some U.S. military analysts said they think that if the Iranians decide on a direct attack, they will rely on the speedboats, which are harder to detect and interdict than the Silkworm missiles.

"It's a threat, but a threat that we can deal with," Sims said. "Our ships have weapons to deal with that threat."

Defense Department officials said U.S. warships escorting the reflagged Kuwaiti tankers would depend primarily on the one 5-inch gun each has aboard.

The Revolutionary Guard has been operating the speedboats mainly from Sirri Abu Musa islands in the lower gulf and from Farsi Island in the northern gulf. But they sometimes use the oil platforms and simple buoys that dot the gulf waters as bases, or dart out on attacks from "mother ships" that are indistinguishable from other commerical vessels in the heavily traveled waterway.

Boghammer has delivered 29 of the 40 boats Iran has ordered, a Pentagon official said. Other news reports said Iran has purchased 50.

Despite the danger posed by the speedboats, the Reagan administration has made no protest to Sweden and has not acted to stop further deliveries under its campaign to prevent arms deliveries to Iran, according to Swedish diplomatic sources and U.S. officials.

"I doubt very much this would be an issue," said one official, noting that such speedboats are not made primarily for military use. "This stuff {speedboats} is available any place," he added.

A Swedish Embassy spokesman said his government does not sell arms to either Iran or Iraq and that therefore the speedboats "could not have been classified as a war item." He said the Iranians had bought the boats in 1984.

The Swedish aluminum speedboat is roughly 42 feet long and driven by twin 305-horsepower diesel engines, giving it a cruising speed of 40 mph and a sprint speed of 60 mph. It has a range of 500 nautical miles, allowing the boat to operate over long distances without refueling.

Because of its light weight, the boat can operate from shallow coastal waters inaccessible to U.S. warships operating in the gulf.

The Revolutionary Guards use five- or six-man crews armed with machine guns and RPG7 rocket launchers and 106 mm recoilless cannons mounted on the stern.

Capt. William W. Mathis, skipper of the USS Fox, one of the three American warships accompanying the Kuwaiti tankers on the first convoy, was quoted in a press pool dispatch as saying the speedboats could carry up to 1,000 pounds of explosives, rocket launchers or recoilless rifles.

He said this is not enough to stop a U.S. warship, "but they really create a lot of havoc and hate and discontent and if they start a fire, that's a big deal."

Sims said the Revolutionary Guard-controlled speedboats have been used in 17 known attacks on neutral ships since February.

Among the recent victims was the Kuwait-bound 273,000-ton Liberian supertanker Peconic, operated by a New York-based company and attacked off Kuwait on July 6. It was hit by at least 18 rockets. They started a fire but caused no casualties.

On July 13, two speedboats attacked the French cargo vessel Ville d'Anvers firing cannons into the engine room and causing enough damage to force the ship to seek repairs at Bahrain.

The Iraqis carried out three raids two weeks ago on several Iranian islands, including Sirri and Farsi, and on oil platforms used as bases for the speedboats by the Revolutionary Guards. Whether the Iraqis succeeded in destroying any of the speedboats has not been reported.