Thanks thanks thanks and many more. It is really great to post a problem and in no time have a huge range of probabilities and cures sent as answers. (1) The mounts are good. (2) cutlass is ok (3) shaft is in line (4) idle speed is maybe only a few rpm
slow. Fix that in the morning. (5) The main problem was a large growth on one side of one blade of the prop. Cleaned that up and all smooth except on idle but that improved as she warmed up.
The seal part of the manecraft thingo is still not concentric to the part attached to the shaft tube but it appears to be ok. Plenty of water from the feed pipe and the shaft tube is full anyway.
Will watch the excentric thing. Once again thanks to everyone. This forum is the best thing I have ever found, apart from my boat.