1989 Johnson Evinrude "CE" Colt/Junior thru 8 Service Manual, P/N 507753, Page 43Get this manual
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 temperature Stop engine Remove and inspect all spark plugs Check 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 compressionis hard to start, AND operates poorly, check for: scored cylinder walls damaged pistons stuck piston rings worn piston rings
I the engine shows variation greater than 15 psi (100 kPa), check for: damaged head gasket damaged pistons broken or stuck piston rings scoredcylinder walls IF the engine has equal compression and runs normally, continue the tune-up procedure3Clean and regap or replace spark plugsMake certain ill ceramic portion of plug is not crackedReplace if cracked to prevent sparks