1998 Yamaha 25J, 30D, 25X, 30X outboards Factory Service Manual, Page 72Get this manual
INSPECTION
G 62501-0
PISTON RING
Inspection 1U sin fe eler e, asure th cle ara nce et th pisto rin and th rin gro eSide clearance: Top ring and 2nd ring: 0.050.09 mm (0.0020.004 in)
If th cle ara nce is ot ithin th sp ecificatio ns, re place th pisto p2n d: ysto ty e