Engine for Nile Gunboat

[RickF]

The drawing below shows one of the two 148 hp engines (or was it two 74 hp engines?) in a "Tamai" class gunboat, ordered in June 1885 from John Elder & Co, Glasgow for the Sudan.

I am finally getting around to building a 1:32 model of "Hafir". As the engines will be partly visible,I would like to add a little more detail than that shown in the drawing - valve gear, for instance - but my knowledge of stern-wheel engines is a bit limited. Can anyone help, or point me in the right direction?

Rick