1981 Johnson/Evinrude 4HP Outboards Service Manual, Page 15Get this manual
TUNE-UP PROCEDURE When an owner brings motor to you for tune-up, or for some minor operating malfunction, the following procedure should be used as guide to determine the cause of the malfunctionWrite down the owner's commentsKeep an accurate card file on your service shop operationEach service operation should be on record as to the: OWNER'S NAME DATE MODEL NOSERIAL NONATURE OF COMPLAINT NATURE OF WORK PERFORMED COST TO THE OWNER PER FOR ME DUN R
If motor shows greater than 15 psi difference check for:sticking ringsworn ringsscored cylindersleaking head gasket If motor has high and continue the tune-upeven compression
A3Clean and regap or replace spark plugsL!!A Make certain ceramic portion of plus is
not crackedReplace prevent sparks
if cracked to