That's David Graham-Smith and his 24 HTM, HP500 mercruiser, there's another older one with a 300 Yanmar.
In the states they run them with massive HP and obviously they are quick, but this side of the pond they don't fair too well.
The one with the Yanmar originally had a 502efi (445hp) when it was new it was tested by one of the Mags at 59mph! So no good unless they've a million hp in em (plus they don't take the rough water too well, and wind up with all manner of cracks/splits, and general stuff falling off)