Mercury Mariner 4, 5 102CC Sail 1990 Outboard Service Shop Manual, Page 62Get this manual
101f necessary, rem ove locator pi ns (a) from cy linder block (b) and rankcase cover (c) Powerhead Cleaning and Inspection
Cylinder Block and Crankcase Cover
IMPORTANT: Crankcase cover and cylinder block are matched line bored assembly and must be replaced as set1Th rough ly clean cy li nde lock and rankcase cove Be sure hat all sea la nt and old gaskets are rem oved rom mati ng surfacesBe sure that carbon deposits are removed from exhaust ports2In spect cyli nder block and rankcase cover for rack and fractu res3C heck gas ket su rfaces nic ks, deep grooves, cracks and istortion hat could cause compression leakages4Chec all water an fue passages in cylinder block and rankcase cover to be su re thai they are not obstruc ted5C heck that all fittings and plu gs are tight