Welcome,The J-9 first appeared in 59 and ran through 68 5hp at 6,800 rpm yes 6,800
You might watch ebay for similar listings.Also look for youtube info from testing or add videos. Try a search on google start by just using Clinton J-9.
You could ask at
www.aomci.org The Clinton and Eska motors aren't exactly
the typical collectable motors but there may be a fan there that can help.
If it was me I would sell the Clinton and put the money toward a Evinrude/Johnson or Gale from 3 to 10 hp. back to the early 1950s.There is a vast supply of new and used parts,decals,paint etc from many sellers, most BRP dealers, here at iboats and even NAPA auto parts stores.Easy to work on and when your done you will have a sweet running motor.Any questions we'll be glad to help.good luck