By 1951 Bogart was one of the biggest stars in Hollywood, enabling him to take a chance in 1948 playing a thorough reprobate in "The Treasure of the Sierra Madre" and getting away with it to public and critical approval; and, yes, he got away with it again in "The African Queen" to even greater acclaim.
It's an amusing performance (easier to take than Hepburn's, at any rate), although it doesn't compare to his work in High Sierra, Casablanca, The Treasure of the Sierra Madre, In a Lonely Place, The Caine Mutiny and a handful of other indelible turns.