Secretary of State Cyrus Vance and British Foreign Secretary David Owen spent six hours today explaining their Rhodesian peace plan to South Africa's skeptical foreign minister, Pik Botha.

Both Vance and Owen told reporters the length of their talks was a "good sign." But there was no indication that Botha, whose country is supposed to pressure Rhodesia's white government to accept black majority rule, liked any part of the scheme.

Vance even said it would have been "inappropriate" to ask the South African for a judgment on proposals that are still incomplete. This was taken to mean that the prolonged meeting here was more of a question-and-answer than a negotiating session.

South Africa, moreover, is only one of many interested and conflicting parties seeking to stop the war by Rhodesia's black guerrillas against the country's white rulers and to end the white minority's monopoly of power.

Rhodesia's blacks themselves are divided among at least four competing leaders. Rhodesia's whites are split over whether any move should be taken toward majority rule. Owen acknowledged today that he did not know where Prime Minister Ian Smith now stood on this central question.

In addition, five neighboring black African states of varying ideological hues are pressing for a black takeover in Rhodesia.

Vance and Owen have refused to discuss the contents of their plan. Its major elements are known to include a constitution giving the vote to the 97 per cent of the population that now lack it; and aid fund to persuade Rhodesia's whites to stay on after they lose their exclusive grip on power: and mixed black-white control of soldiers and police during a transition period until the vote for a new state is held.

Up to now, this last point has frustrated any progress toward agreement. All factions apparently believe that control of the guns will insure their control of the new state.

Vance said that today's talks had produced "good progress in developing the proposals which will be made public in the not distant future." But he and Owen refused to be drawn out about the response from Botha.

The South African did not attend the press conference and neither he nor his aides would comment. Vance indicated that most of the time was spent describing the Anglo-American proposals and replying to Botha's questions about them.

Just as London and Washington hope South africa will press Smith to accept a one-man, one-vote state, the Anglo-American team wants the five neighboring black African governments to bring Rhodesia's black quesrillas into line.

The five, however, have respectedly said the issue must be fought out on the ground.