The merger decision facing executives of Equitable General Corp. of McLean became more complicated yesterday when one of the three-rival bidders made a new offer.

Gulf United Corp. of Jacksonville, Fla., raised its cash offer to $50 per share from $47 and added a third alternative to its two earlier methods of merging the companies.

Equitable General has a $50-a-share offer from Liberty National Life Insurance Co. of Birmingham, Ala., and an agreement to merge with Great Southern Corp. of Houston for $45 a share.

Equitable General has hired First Boston Corp. as its investment adviser in evaluating the three bids, acknowledging that it is considering the Liberty and Gulf offers despite its agreement with Great Southern.

Liberty's offer has been extended through Friday. There is no publicly reported deadline on the other two bids.

Over the weekend, Equitable General announced that its first-quarter net income fell from $2.6 million to $2.5 million, despite record quarterly life insurance sales of $56 million, up nearly 11 percent from the prior year. On a per share basis, quarterly income increased from 81 cents to 87 cents, because the company bought back a large block of its shares earlier this year.

Yesterday's new offer from Gulf United gave Equitable General's board three options, including a straight cash buy-out at $50 a share - about $140 million for the 2.8 million outstanding shares.

The third option, made yesterday is to exchange each share of Equitable General for a unit consisting of one-half share of Gulf United common and one share of a new Gulf United preferred, with a $3.50 annual dividend, but not convertible. Its liquidating value would be $42.

Similar, but less complicated, exchange offers have been made by the other two bidders for the McLean insurance holding company.