It is a dilemma, indeed. Though, since I'm modeling the
African Queen as she was in the film, I think I should have the engine above the deck, as it was in the film, even if I'd rather have the bearings below deck in a whole cut through the deck. Doing that wouldn't be possible, though... you can't sink the engine down enough for it to be on line with the prop shaft. The prop will either be too high and cutting through the stern, or the engine will be too low, sticking through the hull. It would be easier if it was all titled, so the engine could be on deck, with the shaft angled down... (but nooo)
Thanks MV

I've done a fair bit of work on the engine, the engine and boiler is pretty much finished now, apart from a few small things I can do later. The engine's all dirty, and I've added the hose and the taps (valves?) that connect the hose to the engine and boiler. The whistle is also in, as you can see.

Click here to enlarge