PS, bit more info on it on the dreaded Wikipedia. Seems the original boat from the movie is restored and on display in Florida.
Filming was actually done in Uganda and Congo, and the boiler was a copper fake, according to Wiki.
"Most of the action takes place aboard a boat – the
African Queen of the title – and scenes on board the boat were filmed using a large raft with a mockup of the boat on top. Sections of the boat set could be removed to make room for the large
Technicolor camera. This proved hazardous on one occasion when the boat's boiler – a heavy copper replica – almost fell on Hepburn. It was not bolted down because it also had to be moved to accommodate the camera. The small steam-boat used in the film to depict the
African Queen was built in 1912, in England, for service in Africa. At one time it was owned by actor
Fess Parker.
[14] In December 2011, plans were announced to restore the boat.
[15] Restoration was completed by the following April and the
African Queen is now on display as a
tourist attraction at
Key Largo,
Florida.
[16]
Because of the dangers involved with shooting the rapid scenes, a model was created at the studio tank in London."
Nice video of the boat in action today, showing some good close up shots of the engine in action
[ame]https://www.youtube.com/watch?feature=player_embedded&v=fiHPaNktEGM[/ame]