1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 187Get this manual
Cleaning, Inspection and Repair All Models Cylinder Block and Crankcase Check cylinder walls for excessive wear and check cylinder ports for carbon accumulationCylinder walls wear in various degrees, depending on lubrication and conditions under which the motor is operatedMajor portion of wear is in the port area and the area covered by ring travel632 10
Check cylinder for size and wall straightness by using an inside micrometerReplace cylinder block, or rebore block for oversize pistons if wear is in excess of specifications in chart below
Model 65 100 and 155
Maximum Tolerance 0.003" (0,08 mm) 0.004" (0,10 mm)
Oversize pistons and ring sets are availableCarbon accumulation in the exhaust ports restricts the flow of exhaust gases and has considerable effect on performance of the motorCarefully scrape carbon from cylinder heads and exhaust ports with scraper or other blunt instrumentExhaust ports and all exhaust passages must be free from carbon deposits to insure maximum performanceAvoid getting carbon in water jacketsWith continued operation of the motor, the cylinder walls wi ll take on glaze which reduces the effectiveness of the seal between the piston rings and the cylinder wallsThe result will be reduced compression and decrease in performance of the motorBefore reinstalling the pistons, break the glaze by using fine cylinder hone to refinish cylinder wallsUse low rpm on drill with rapid up and down movement to obtain good crosshatch pattern for good oil retentionUse hone with medium stone (220 grit)Blowout all oil passages and drains