1972 Johnson 4HP Outboard Motor Service Manual, Page 42Get this manual
EXHAUST
Figure 5-15Checking Ring
Figure 5-17Correct Piston Position Apply coat of to wrist pin, making sure surface is cleanPlace drop two of in each pin hole in the pistonInsert wrist pin through slip fit side of pistonwrist pin bearing in connecting rodPlace connecting rod in position, then proceed to install the wrist pinThis accomplished easily if the piston is heated slightly, causing it to expand
Figure 5-16Checking Ring Groove Clearance
REASSEMBLY OF POWER HEAD