2001 Edition Yamaha F225A and LF225A Outboards Service Manual, Page 145Get this manual
Cylinder block Piston diameter a: 93.92193.941 mm (3.69773.6985 in) Measuring point b: mm (0.2 in) up from the bottom of the piston skirt
Checking the piston clearance
1Rebore the cylinder or replace the piston and piston rings as set, or the cylinder block, or all parts if out of specificationPiston clearance: 0.0750.080 mm (0.00290.0031 in)
Checking the cylinder bore
1Measure the cylinder bore (D1D6) at measuring points a, b, and c, and in direction (D1, D3, D5), which is parallel to the crankshaft, and direction (D2, D4, D6), which is at right angle to the crankshaft
Checking the piston rings
1Check the piston ring dimensions of and TReplace if out of specification