Mercury Mariner 4, 5, and 6HP 4-Stroke Factory Service Manual, Page 123Get this manual
CYLINDER HEAD
VALVE SEAT RECONDITIONING Clean the carbon deposits from the combustion chambers and valve seats and check for pittingSeveral different types of equipment are available for reseating valve seatsFollow the equipment manufacturer's instructionsMeasure valve seat widthResurface the valve seat if not in specification
aValve Seat Width Valve Seat Width Specification "a" Standard Value Intake Valve Seat Exhaust Valve Seat 0.031 in(0.8 mm) 0.031 in(0.8 mm) Limit that requires repair 0.070 in(1.8 mm) or more 0.070 in(1.8 mm) or more