think that 7.5 can be changed to a 9.8 with a carb swap. same cc's. if you need a carb I work for a mercury dealer. and if its still got a two blade prop try the three blade they offered. still can get parts for them antiques
skeg is missing some material. but find someone that welds aluminum and that should be a cheap fix. my old 65 looks like that but still runs 50mph on my boat.
does it have a choke primer? if so get the engine running and make sure your not getting fuel flowing out of your smaller fuel lines. and starting fluid is a good way to replace reeds.
I've got a tester that test condensers. but I'm in ga. and coils lol! working on boats is what I do full time so I've got a lot of old test equipment. maybe points gap?