Thirteen House Democrats yesterday sent a "Dear Colleague" letter to all House Democrats urging that Rep. Robert L. F. Sikes (D-Fla.) be ousted as chairman of the Military Construction Subcommittee of the House Appropriation Committee.

The House voted 381 to 3 last year to reprimand Sikes after a House ethics committee investigation concluded that he had "violated standards of conduct" by using his official position for personal benefit.

The ethics committee, among other things, found that Sikes had sponsored an succeeded in getting passed legislation that removed restrictions on commercials development of certain properties in Florida. Sikes did not disclose that he had financial interest in the property. He made a substantial profit because of the legislation.

The "Dear Colleague" letter said the subcommittee chairmanship should not "be filled by any member against whom sanctions have been imposed by the House . . . especially . . . when key violation derive from misuse of the power of the very chairmanship which is at issue."

Signers of the letter included Rep. Richard Bolling (D-Mo.), a senior member of the Rules Committee; Black Caucus Chairman Parren J. Mitchell (D-Md.) Rep. Donald M. Fraser (D-Minn.), who is currently chairing a subcommittee looking into aspects of the Korean influence-buying scandal; Rep. Don Edwards (D-Calf.); Abner J. Mikva (D-Ill.) and Jonathan B. Bingham (D-N.Y.).

Rep. Andrew Maguire (D-N.J.), the principal drafter of the letter, said, "I don't see how we can say we are serious about a new, tougher code of ethics unless we act" on Sikes.

Chairmen of all standing House committee must be elected by the Democratic Caucus, the organization of all House Democrats. But the Appropriations Committee is the only committee whose subcommittee chairmen must be elected by the caucus. A vote is likely on Jan. 24.