Someone should have thrown in the towel on "The Prizefighter," a film that teams Don Knotts and Tim Conway as two ringside bumblers who get involved in underworld manipulations.

Conway, who was a good funnyman foil in those hilarious skits on the Carol Burnett television show a few years back, also wrote the story and worked on the movie script. Apparently, the TV prelims didn't train him for the rigors of a full-length movie.

It's set in the era of gun molls, hit men and speak-easies, and the best things about the film are the classic old autos -- including a magnificent Rolls.

Knotts and Conway -- who plays an ex-boxer with a perfect record of 20 losses in as many fights -- are fight-world hangers-on who are picked up by a smooth gangster chieftain who either has a bad case of laryngitis or is imitating Marlon Brando in "The Godfather."

The gangster wants control of some property. He plans to put Conway into some fixed fights and arrange a bet in which he will win the property from a stubborn gym manager. Pops Morgan (David Wayne, an old pro, must have been down on his luck to take the role of Pops.) Pops wants to keep the place for the orphaned boy he is raising. The rest of the script is not hard to imagine, although the comedy is.

Sight gags and pretialls can't fill nearly two hours on the screen, and they aren't that good to begin with: For example, a towel is thrown into the ring with a water bottle to conk the referee; an old lady pops out of a grandfather clock and stuffs a green onion in the ear of a guest. The film, showing at several area theaters, deserves a quick and early knockout.