Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 87Get this manual
Use piston ring expander tool (91-24697) and install piston rings (a) on piston Lubricate cylinder bores with light oil
Lubricate rings with light oil and align ring ends with locating pins as shown
Recheck piston ring end gap alignment with locating pinsInstall ring compressors on pistons as shown
Piston Ring End Gap Location (Correct)