Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 143Get this manual
Piston with two half keystone (half tapered) rings
Crankshaft
12Inspect crankshaft to drive shaft splines for wear(Replace crankshaft, if necessary Check crankshaft for straightnessMaximum runout 0.002 in(0.050Bmm) Check runout at center main bearing surfaces with ends of crankshaft supported in v-blocks(Replace as necessary Inspect crankshaft oil seal surfacesSealing surfaces must not be groovedpitted or scratched (Replace as necessary
MEASURING PISTON ROUNDNESS Piston has barrel profile shape and is not true diameter1Using micrometer, measure dimension "A" at location shownDimension "A" should be as indicated in chart followingPiston Standard Piston .015 inOversize Piston 2Dimension "A3.6210 in.0005 in3.636 in .0005in
4Check all crankshaft bearing surfaces for rust, water markschatter marks, uneven wear andor overheating(Refer to Rods"
If necessary, clean crankshaft surfaces with crocus cloth
Using micrometer, measure dimension at location shownDimension should be 3.6210 in A" 0.0005 infor STANDARD size piston