SAN FRANCISCO (AP) _ A man described by his attorney as ''a boat thief, but not a murderer'' has been convicted of killing a wealthy San Diego woman in 1974 on an isolated South Pacific island.

Jurors deliberated just two hours Tuesday before finding Buck Duane Walker, 47, guilty of the first-degree murder of Eleanor ''Muff'' Graham, of San Diego.

Mrs. Graham, whose burned bones were discovered at Palmyra atoll in 1981, had been on a cruise with her husband, Malcolm, in their yacht and disappeared after they stopped at the horseshoe-shaped island about 1,000 miles south of Honolulu. No trace was found of Graham.

Walker ''murdered Muff Graham to get the (Graham) sailboat and its supplies,'' U.S. Attorney Elliot Enoki told the jury, adding that Walker's own boat, Iola, was leaking badly and carried dwindling provisions.

''The motive is so strong it about overwhelms the rest of the case,'' he said.

Defense attorney Earle Partington vowed to appeal, saying he was surprised at the speed of the jury's verdict and accusing U.S. District Judge Samuel P. King of ''assisting the prosecution'' with his rulings during the 11-day trial.

Partington called Walker ''a boat thief, but not a murderer.''

Walker could receive a maximum sentence of life in prison. Sentencing was set for June 28.

''I'm glad to see justice was done after all this time,'' said U.S. Justice Department Trial Attorney Walter E. Schroeder. ''Muff Graham went a long time without retribution.''

Enoki had reminded the jury of testimony that Mrs. Graham had once broken down in tears and told others on the atoll she feared she ''would never leave the island alive.''

The Grahams had sailed their 37-foot yacht Sea Wind around the world and lived on it all year, Enoki said, describing the couple's last cruise and their landing in July 1974 inside the lagoon at Palmyra, an occasional port- of-call for yachts cruising the South Pacific.

Walker and his girlfriend, Stephanie Stearns, tried to sail the Iola into the lagoon but ran aground and had to be helped in by other boats, he said.

By late August, the only yachts left at Palmyra were the Iola and Sea Wind, and the two couples ''did not get along ... they were barely associating,'' Enoki said during the trial.

Walker and Ms. Stearns, 37, were arrested after sailing the Sea Wind to Honolulu and were convicted in separate trials of its theft. Walker was sentenced to 10 years in federal prison and Ms. Stearns served a two-year term. Ms. Stearns faces trial later this year in Mrs. Graham's slaying.

''I'm pleased,'' Graham's sister, Kit McIntosh of Seattle, said after the verdict. ''My brother wrote me from the island about what was going on - the tension. There was no way you could get my brother's boat without killing him.''