1975 Evinrude 40 HP Outboards Service Manual, PN 5093, Page 50Get this manual
Check cylinder for size and wall strai ghtness by usin an inside mi crometer or dial bore indi catorRefer to Section for specified dimensionsReplace cylinde blockor rebore block for oversize pistons if wear is in excess of .003"Pistons and ring ets are available oversize Uml NOTE ll'f
If your shop is not equipped to rebore cylinder blocks, write our Service Department about our reboring service
Carbon 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 performance
Figure 5-15"LOOSE" Mark on Piston