Mercury Mariner 4, 5 102CC Sail 1990 Outboard Service Shop Manual, Page 63Get this manual
Cylinder Head , Inspect cylinder head for cracks, carbon build up or other damage2Use surface plate and feeler gauge to measure cylinder head wa rpageCheck al several poi nts around diameter of head31f cylinder head measurement is out of specifi catio listed in chart followingreplace headSmall pits,
Hose and Check Valve
Hose removed during disassembly has check valve as shown The va lve allows one way passage of crankcase res iduals
To Check:
I -!-I 125.4 mml
burrs and other similar damage can be removed
starting with 320 and end ing with 400 grit crocus cloth on surface plateRecheck head as desc ribed in step 2, preceding prior to placing cy linder head in servicea Check Valve