Defense Minister Ezer Weizman told Israelis today that Egyptian leaders seem "sincere" in their desire for a Middle East peace, but he cautioned: "It's not going to be a smooth ride."

Using pilot's language, the former commander of the Israeli Air Force said he felt the outlook was for "a few clouds, a bit of sunshine, a bit of rain, a bump here and a bump there."

Weizman's cautious appraisal following two days of talks in Egypt with President Anwar Sadat and War Minister Abdel Ghani Gamasy contrasted sharply with the more upbeat tone of reports emanating from Cairo.

The Iraeli defense minister emphasized, however, that he remained hopeful. "I would not say I am optimistic," he told reporters at Ben Gurion Airport, "but rather that I am full of hope as to the outcome of the Cairo negotiations."

Weizman declined to discuss with reporters any details of his meetings in Egypt before briefing Prime Minister Menahem Begin.

Weizman's trip to Egypt underlines the way in which Foreign Minister Moshe Dayan, with his known private doubts about the wisdom of the current furious pace of developments, is being put in the background.

There is even said to be some doubt remaining about whether Dayan will accompany Begin when he goes to Egypt Christmas Day. Begin seems to be using Weizman deliberately as a counterweight to Dayan.

Upon his return from abroad latelast night, Begin said: "We are now keeping up the fast pace of the negotiations. They are bound to be fast because this is the propitious time for peacemaking in the Middle East."

Dayan has recently indicated that he would find the prospect of a separate peace with Egypt attractive. On that basis, Begin and Dayan can probably resolve any tactical differences they have.

But there have been president reports from friends and collabroators of Dayan, who has been keeping an unusually low profile, that he has been in a foul mood ever since Sadat's dramatic trip to Israel Nov. 19. Dayan's departure from the Begin government would probably be the worst blow Begin could receive in his drive to gain acceptance at home for concessions to be made in exchange for peace.

The prime minister is scheduled to spend the rest of the week mending his political fences at home, before going to see Sadat in Ismailia on Sundays.

He will finally give the full Cabinet the details of his peace plan Thursday. The nex day, he will speak to the Foreign Affairs and Defense Committee of the Parliament and have a session with the deputies of his own Likud bloc o right-wing parties.

They have been displaying the most anguished doubts about Begin's apparent abandoment of Likud's ideological commitment to making the West Bank part of Israel proper. Doubts among Likud deputies are said to run deeper than anything that has so far been said publicly.

Begin's new position is that the area should not come under the sovereignty of Israel or of neighboring Jordan, which ruled the West Bank for 19 years before losing it to Israel in the six-day war of 1967.

Members of Gush Emunim, the militant rightist group in favor of settling and annexing the West Bank, served notice that it plans to demonstrate outside the building while the Cabinet is in session Thursday.

Weizman reported tonight to the only group of ministers that has been kept in the picture by Begin, the Ministerail Security Committee. Dayan, who is a member of the group, has made some remarks indicating that he is not entirely certain that Begin has told them everything.

Also at the two-hour meeting chaired by Begin were the two major generals Weizman took with him to Egypt, Sinai Commander Herzl Shafi and Military Intelligence Director Shlomo Gazit.

Weizman flew to Egypt yesterday and returned in a DC-9 supplied by the U.S. Air Force. Weizman said he would have kept his whole trip secret if the Egyptians had not leaked it to the press.

Israeli officials said the reason for asking the Americans to loan the plane was to maintain the secrecy. State Department spokesman Hodding Carter said it was flown by an Egyptian crew.

Weizman said that he discussed the creation of hot lines between Israel and Egypt. According to Israeli press reports there is already a temporary open teleprinter between the office of Sadat and Begin.

The Israeli state radio said that Weizman also suggested a major reduction of Israeli and Egyptian forces in the Sinai.

Weizman told reporters that his discussions had been entirely about the Sinai and that his mission was to prepare the ground for the Sadat-Begin encounter. That tends to lend weight to the notion that Egypt and Israel are seeking a separate deal which Israel's other Arab neighbors could join later in separate negotiations and with separate peace agreements.

The Israelis are reportedly asking to keep an early-warning station in Sinai and to maintain American monitoring stations there while reducing the role of the United Nations.

Meanwhile, there was fairly universal dismissal here of reports from the United States that President Carter had told Begin that his proposals for the West Bank would be unacceptable to Sadat. The Israelis did back away, however, from previous official statements that there was an "identity" of views between Carter and Begin.The Israelis keep stressing that their proposals are basis for negotiations rather than a take-it-or-leave-it final offer.