Thank you,I was sure I had a major problem until I noticed the top spark plug had no gap,it would appear that it was running on 3 cylinders causing rattle.
driving at 4000 revs sudden noise like loose part (metal sound)stoped and checked all looked ok, restarted no problems but noise remained.
At home started with ears on,no noise (no water pressure on prop)
Should I be looking for a bearing problem or broken part in the gear box or some other...