The National Park Service is inviting proposals to take over three marinas along Lake Powell but any would-be concessioners should know they're playing against a stacked deck.

The marinas are all in Glen Canyon National Recreation Area. They are Bullfrog, in Kane County on the western shore of the lake, accessible by Utah 276 south from Hanksville; Halls Crossing, on the Arizona side of the lake and connected to Bullfrog by a ferry; and Hite, on the northern end of the lake in San Juan County.The deck-stacking is due to the federal law concerning National Park Service contracts. "Existing concessioners who have provided satisfactory service are provided a right of preference in the renewal of contracts by law," said NPS spokeswoman Marsha Karle, Denver.

"Due to its previous satisfactory performance, Del Webb Recreational Properties Inc. enjoys this right of preference."

The Park Service will provide a fact sheet on requirements for running the marinas.

The contract for Hite and Bullfrog expired on Dec. 31, 1987, and that for Hall's Crossing will expire on Dec. 30, 1990. The Park Service wishes to combine these into a single contract.

Anyone interested in submitting proposals to run the marinas should send them to the Park Service by June 25. The address is National Park Service, Rocky Mountain Regional Office, P.O. Box 25287, Denver, CO 80225-0287.