Anyhow , long storey short ( for a change  )  , this thing was last run 2 years ago  , in salt water , taken home where the decision was made to not use it  any more   and it was parked without any flushing ( apparently the PO was quite diligent up to this point ). Fortunately a son in law had the presence of mind ( some time later ) to make up a stiff brew of fuel  and started the engine ,  without any water   and choked it to death with 2/ oil  .......and the bore scope sez he did a good job . 

 I want to run it in a tub full of something that will dissolve the salt and any corrosion . Id be happy to run it for a day if it works 

 What is the best stuff to use   ( I am Kiwi  so I will at least double the recommended  concentration  ).