1983 Yamaha 30EN Outboards Service Manual, Page 64Get this manual
2 Remove any deposits from cylinder exhaust port
5Using cylinder gauge set to standard
bore size, measure the cylinderMeasure front-to-rear and side-to-side at top, center and bottom just above exhaust portTake minimum and maximum measurementsIf over tolerance and not correctable by honing, rebore to next over-sizeMaximum allowable taper: 0.08 mm (0.003 in) Maximum allowable out-of-round: 0.05 mm (0.002 in)
3Check the cylinder body water jacket
, and cooling water passages for dirt, salt, sand, and other deposits, and clean, as requiredAlso patch up any part from which anti-corrosion paint has come offIf the water jacket or passage is corroded, replace the cylinder assembly (cylin der body and crankcase)