1996 Johnson/Evinrude Outboards 8 thru 15 Four-Stroke Service Manual, Page 35Get this manual

1996 Johnson/Evinrude Outboards 8 thru 15 Four-Stroke Service Manual, Page 35

Tune-Up Procedure 1Visually inspect engine for leaks, missing or loose parts, or other obvious defects2Compression checkProper compression is essential for good engine performanceAn engine with uneven compression cannot be properly tuned Operate the engine until it reaches normal operating temperatureStop engine Remove and inspect all spark plugsCheck their condition Install thread-type compression tester in spark plug hole With throttle in wide-open position, crank engine with starter through at least four compression strokes Variation between cylinders should not exceed 15 PSI (100 kPa)IF the engine has equal compression, is hard to start, AND operates poorly, check forscored cylinder walls damaged pistons stuck piston rings worn piston rings

IF the engine shows variation greater than 15 PSI (100 kPa), check for: damaged head gasket damaged pistons broken or stuck piston ri ngs scored cylinder walls burnt exhaust valves