Congratulations - you have made a sound investment!
We have completed just under a thousand miles this year with our K3 including the Severn Estuary and Tidal Thames. Fuel consumption has worked out at less than 2 litres an hour on average and is usually half this on canals. There is no visible smoke exhaust (except when revving in reverse for an unplanned stop) and the rythm of the engine is always an absolute delight. Our only major problem was the failure of the CAV diesel injection pump - one of the few components not made by Kelvin!
If we may be permitted to offer a few words of advice; our prop is a three bladed 24" X 24" and this works very well for us - giving about 8 Knots at 600 rpm on rivers and a sensible 4 mph at 300 rpm on most canals. It is small enough to slow us down to less than 2 mph at tickover when passing moored boats and large enough to stop the boat in half its own length when necessary. We have adjusted the regulator stops to limit the engine to 600 rpm with a minimum idle speed of 120 rpm - it will go slower but there is a danger that at very slow speeds, insufficient lubrication will reach those 9 inch bores.
We did a lot of research into boat builders and from a short list that included Barry Hawkins and Roger Fuller, we settled on R W Davis. In the event we were able to buy our boat secondhand thrpough R W Davis - it was Phil Trotter's prototype - now ten years old and we are totally satisfied with it. The build quality of the 'Northwich Traders' would be difficult to match anywhere and the way the boat handles makes us look like experienced professionals. Phils knows how to build a superb vessel and although not cheap, you would certainly get good value for money - he also has knows how to install a Kelvin engine properly.
Good luck with your project!