Here is what iboats.com has to say about them – note displacement is 10 cu inches:
Dave
1981 Johnson 7.5 HP
8RCI
This 7.5 H.P. Johnson outboard motor was made for the saltwater environment. The piston displacement is 10. The bore and stroke are 1.93" and 1.70" respectively. This outboard has starter of the recoil type.
Serial Number: CI
RPM Information: 5000
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