Thanks for all of the suggestions. Having spoken to a couple of engine guys today I might stretch my budget a bit more so its between four stroke and new tech two strokes, but I do not want to start a debate on that front I am sure that there are plenty more threads on that!
150hp optimax sounds great, but may be just too much power.
What I want to do is cruise comfortably at 30 kts and push towards 40kts occasionally, whilst keeping some degree of economy. There is no point putting too much power on the boat as there are few times when the conditions allow you to run fast for extended periods.
Mmmm must keep pondering on this one. Any more suggestions appreciated.