Re: Which impeller
1983 model.
no gasket but worth dismantling to see if it is worth buying the complete repair kit
Also surprised a bit by the model number. Are you in the UK? You are aren't you?
Outboards direct ( aka Oakley Marine) in Brighton or Willsmarine in Kingsbridge, Devon are both good for spares.
Quote the model number and they should be able to sort you out.
I think the impeller number will be 0389576 but check