The votes of white missionaries prevented the election of the activist South African clergyman, the Rev. Allan Boesak, as president of the colored, or racially mixed, branch of the Dutch Reformed Church in Capetown this week.

In August, Boesak was elected the first nonwhite president of the World Alliance of Reformed Churches, in a historic session that also suspended two white South African Reformed Churches from membership because of apartheid policies of the white denominations.

Boesak, a university chaplain, lost the race for president of his church by seven votes. Of the 528 voting delegates at the church's quadrennial synod, 93 were white missionaries, who tipped the balance in favor of a conservative candidate, the Rev. Izak Mentor.

Boesak's defeat was seen as a setback for his campaign to put moral pressure on South Africa's ruling white Afrikaaners to modify the country's strict segregation system.

Boesak, who was elected deputy leader of the church, said he would try from that position to get the synod to endorse the World Alliance's declaration that apartheid is a heresy and to cut ties with the white church. Mentor said he would oppose this move.

Earlier in the week, one of the white churches suspended from the World Alliance, withdrew from that body. The Nederduitsch Hervormde Kerk said it could not comply with the Alliance's request to renounce apartheid.

In a related development, the National Council of Churches in New York and its member communions gave a $55,000 grant to Bishop Desmond Tutu, as an act of solidarity with the South African Council of Churches, which he heads. Tutu and the South African church council, the only national forum for expressing black grievances against apartheid, are currently the focus of an investigation by a special commission of the South African government.