Hi. It looks complete to me. Try connecting some compressed air through the port on the top of the cylinder as that is where the ports are on the slide valve and this should tell you something. You may need to spin the flywheel to get it moving. Cheers Ian

You have a PM Research horizontal mill engine there. Not really suitable for incorporating into a model boat. As it is only a single cylinder engine it won't self stare easily and there is no way to reverse it without modification. You would also need a fairly large boiler to keep it in steam, as it is a fairly heavy cast iron job it will take a fair bit steam to keep it going... Here is my example...

It would be difficult to fit it in as the engine is at right angles for the prop shaft. Could be a little on the wide side for a paddle boat as well. I have asked my friend Malcolm if he can identify it.

Apart from a steam pipe and a displacement lubricator you need a boiler and burner. Size of boiler would depend on bore and stroke of the engine. The valve gear shows it is double acting and would self start.
I would guess it is quite heavy so a boat might not be the best place for it.

How long is it?
Roy