A tug and barge company and its insurers have agreed to pay close to $6 million to resolve a lawsuit involving the 1985 loss of a boat off the coast of northern California, in what may be the largest out-of-court settlement of its kind.

Five crewmen and a passenger died in the accident. Settlements to the various estates included sums of $4.5 million, $1.1 million, $870,500 and $60,000.The defendants in the case were offered a pretrial settlement far below the amount eventually agreed on but turned it down. Philadelphia attorney Marvin Barish, who negotiated the $4.5 million settlement, said he offered to take $750,000 earlier in the case but was turned down.

The settlement was reached March 16, two days after the case went to trial.

It's by far and away the largest settlement of its kind, said Forrest Booth, an attorney with Hancock, Rothert & Bunshoft, which represented the boat owner and the insurance companies.

The accident occurred off Point Arena, Calif., in the early morning hours of May 2, 1985, and took the lives of all six people on board the vessel, the Willamette Pilot 3.

Western Tug and Barge, a division of Reidell International Inc. of Portland, Ore., owned the vessel. The property and indemnity insurer, which was not named in the suit, was Lloyd's of London, which covered only the passenger. The primary underwriter on the marine operators liability insurance was National Union, an affiliate of the New York-based American International Group, which also was not named.

The Coast Guard said it received a distress call at about midnight May 1 saying the pilot boat was listing, Mr. Booth said.

Fourteen minutes later the Coast Guard received a second call from the vessel indicating that the list was then 25 degrees starboard in the direction of the stern. That was the last word heard from the vessel, Mr. Booth said.

The water in the area is about 10,000 feet deep and the only object recovered was a circular life ring that had evidently plunged down with the vessel before returning to the surface, Mr. Booth said.

It looked like a raisin. The pressure had collapsed it. It was all misshapen, he said.

Tom Boyle, an attorney with the San Francisco firm Sullivan, Johnson, Boyle & Nurik, which represented one of the victim's estates, said a sister ship, the Gulf Gale, which sank about a year earlier in shallow water, had experienced stability problems.

The testimony of a port engineer established that the owner of the Willamette Pilot 3 knew about the earlier incident but went ahead and sailed anyway, Mr. Boyle said.

But Mr. Booth said the sister ship had been substantially modified without performing any subsequent stability tests and no longer had the same design construction.

Mr. Booth said no one knows exactly why the ship went down. He said an engineering consulting firm was hired to try and recreate the reported list. They determined that it would have taken a flooded aft ballast tank and possibly an open hatch to replicate the list but that this still didn't explain the sinking. It's a very difficult thing to determine, he said.

Mr. Barish said the case turned on the fact that the crew was inadequate in number and in experience. It was crewed in violation of U.S. codes, which require able-bodied seamen with officers not working greater than 12 hours, he said. The vessel was also too low in the water, and there appeared to be a problem with the docking nuts.