I have a Wizard 7.5 hp that I need info on. Motor is made by Tecumseh. Model number on engine is 640-07A, serial number 7476408. Year, oil mixture, where to find part, and the like would be greatly appreciated.
You have a 1975 air-cooled Wizard made by Eska Outboards. These are the same as the Ted Williams outboards sold at Sears during that period, along with those marketed under the Eska brand name. It has a Tecumseh powerhead that is pretty much the same as a lawnmower powerhead. Some parts are available through Certified Parts Corp. and http://www.discount-marine-parts.com/ob_eska_wizard.html. There also seems to be a lot of Eska parts available on Ebay. That model does have an impeller, but it is simply for cooling the lower leg....it doesn't cool the powerhead. Oil mixture is 24:1, and you can use TCW-3 marine oil.
Personally, I wouldn't sink a lot of money into an Eska. Parts are going to be a little on the expensive side as they become more harder to get. That said, if you can get it running easily it may make a nice fishing motor. They are nice and light weight for the HP.