Welcome to the new Wizard Outboard Forum.
I have the exact same motor. Plugs are hard to find by the original number, but replacements are available. The original was a Champion H-8-J
A .PDF file of the manual is available:
Go to: http://search.ebscohost.com/
Log in with:
User ID: marshall
password : public
-----Go under the Small Engine Repair Reference Center (look for the wrench), then Marine/Boat Motors....you will click on Chrysler in the 3rd column and then click on "AIR COOLED 3 1/2 HP".