In my opinion a running 5.5 hp Johnson for $100 is a steal especially with the gas tank. Gas tanks that are in working condition with good paint go for over $100 on ebay.
I really like the old Evinrude and Johnson 5.5 hp motors. My 1957 model Evinrude 5.5 hp Fisherman is the best running motor I own and in my opinion the best looking. I really don’t like the looks of the later model motors with the plastic cowling.