A California sailor who embarked on a solo voyage across the Pacific dedicated to saving the whales called off the effort today after an encounter with two whales.

The sailor, Michael Reppy of Sausalito, set out on May 10 seeking to set a record for a solo sail from San Francisco to Yokohama, Japan. The trip was intended to publicize the plight of captive whales and the slaughter of dolphins by Japanese fishing fleets.

One day out, Mr. Reppy reported that two whales ''blew by'' his 60-foot ocean racer, ''Thursday's Child,'' almost ripping off the rudder. While he initially believed no serious damage had occurred, the boat became increasingly difficult to control. On Thursday, he found that the bottom of the rudder was gone, presumably knocked off by one of the passing whales.

Mr. Reppy said he was headed for Honolulu, about 900 miles away, where he would assess his options. His last solo trans-Pacific voyage, a 1997 effort also mounted to draw attention to the plight of marine mammals, ended when his 36-foot trimaran capsized about 300 miles from the planned finish in Tokyo.