Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 79Get this manual
Inspect crankshaft bearing (a) Cleaning and Inspection
Cylinder Block
Inspect cylinder bores for scoring (a transfer of aluminum from piston to cylinder wall)Cylinder wall scoring usually can be "cleaned up" by honing or reboring Hone all cylinder walls just enough to de-glaze wallsMeasure cylinder bore diameter (with an inside micrometer) of each cylinderas shown belowCheck for taperedout-of-round ("egg-shaped") and oversize boreIf cylinder bore is taperedout-of-round or worn more than .006 in(0.152mm) from standard "Cylinder Block Finish Hone" diameter (refer to chartpreceding)it will be necessary to rebore that cylinder(s) to .015 in(0.381 mm) or .030 in(0.762mm) oversize and install oversize piston(s) and piston rings during reassembly NOTE: The weight of an oversize piston is approximately the same as standard size pistontherefore, it is not necessary to rebore all cylinders in block just because one cylinder requires reboring After honing and thoroughly cleaning cylinder bores, apply light oil to cylinder walls to prevent rusting CYLINDER BORE SIZE Piston Size With Standard Size Piston With .015 inOversize Piston With .030 in Oversize Piston Cylinder Block Finish Hone 2.875 in 2.890 in 2.905 in