Marriott Corp. stock increased in heavy trading yesterday, primarily from two blocks of 100,000 shares each traded by the New York investment firm of Morgan Stanley & Co., Inc.

The second most active issue on the Big Board, Marriott jumped 87 1/2 cents to $11.50 on a volume of $365,900 shares.

A spokeswoman for Marriott and an official of Morgan Stanley said they knew of no unusual circumstances behind the two large transactions yesterday.

Several Wall Street analysis noted, however, that there has been renewed interest in the Bethesda-based lodging and restaurant company since a cash dividend policy was announced at the anual meeting here last month.

Two recent reports from stock analysis forecast substantial gains in profits for the current fiscal year. Donaldson, Lufkin & Jenrette this month estimated Marriott annual earnings would rise to $1.18 a share while Johnston, Lemon & Co. has increased its forecast of earnings to $1.25 a share from $1.15.

In the year ended last July 29, Marriott earned $36.1 million (99 cents) on sales of $1 billion.

A former so-called galmor issue, of a company that has exceeded annual growth rate goals of more than 15 per cent in both sales and profits for many years, Marriott stock has plummeted in the 1970s.

Marriott's stock hit a two-year low of $8,75 in November, prior to the announcement that a small cash dividend (starting at 3 cents a share quarterly on Jan. 15 to owners of record Dec. 30) would replace annual stock dividends that ranged from 2 per cent to 4 per cent.

The stock price has been moving higher ever since although it is still is below the 1977 high of $13.625. In 1976, Marriott traded in a rage of $12 to $18.15.

Troubles in the Farrels ice cream parlor division, which since has regained profitability; lower-than-anticipated theme park attendance and the absence of cash payouts had been cited by analysts as factors in the lack of investor interest in Marriott earlier this year.

President J. W. Marriott Jr. told the annual meeting that the outlook for fiscal 1978 is "excellent." The firm reported a 28 per cent jump in profits in the quarter ended Oct. 21 on a sales increase of15 per cent.