The shovel bladed prop on the S.S Great Britain was later replaced with a more conventional looking four bladed propeller. This proved to be considerably more efficient.
I believe that Brunel, and his design team, benefited from the work of an engineer called John Ericsson, the designer of the Monitor, a ship that needs no introduction and also the original inventor of the ship propeller.
I've seen the Great Britain prop up close, it's a pretty impressive piece of work (a replica though).
The design is good enough for model use, but it isn't as efficient as modern designs.
A footnote, most folk acknowledge that anymore than three blades on a model prop leads to greater inefficiency.
Edited By Sub culture on 1061635201