I have a 1939 CE in my 57'8" narrowboat - India Number 1. It's a superb engine that turns heads with its mellow tone and resonance and is quite able to travel all of the UK's navigable rivers. In the twelve years of ownership it hasn't missed a beat although, like others, I have acquired a 'spares or repair' CE to keep in the garage just in case something gives up the ghost. If you're ok about relaxed cruising- it's obviously not as powerful as a JP2- I personally wouldn't hesitate to recommend one.
