1971 Johnson 4HP Outboard Motors Service Manual, Page 29Get this manual
CLEANING, INSPECTION, AND REPAIR SPARK PLUGS Inspect plugs for cracked porcelain and worn electrodesClean the electrodes with point DO NOT sandblast spark plugsAdjust gap to the specified .030 inchIn re-gapping, adjust only the ground electrode, as attempting to bend the center electrode will crack the insulatorSee Figure 4-7motor performance and premature spark plug failure result from improper spark plug installationBefore installing the plug, sure the plug seat in the cylinder head is clean and free from obstructions See Figure 4-8Install new spark plug gasket, Screw the plug in hand, then tighten to the specified 17-1 to 20-12 foot pounds165 4
Figure 4-8Cleaning Spark Plug Seat
If threads
stripped in cylinder head, coil inserts availableCaution should taken when installing Heli- coil insertsTools and inserts available from parts distributorCLEANING POINTS
After extensive service, the breaker points worn, dirty, out of adjustmentInspect the breaker assemblies forcorrosion unusual wearQuestionable breaker points should placedCheck action of the spring and free movement of the breaker Do not change breaker spring tensionDirt, foreign particles, and very detrimental to .contact performanceoils and acids from hand, even though clean, affect contact resistance deposits the points will them to out after very short period of operationNEVER FILE POINTS - replace themremove traces of dirt from contacts, insert strip of bias tape dipped in alcohol trichlorethylene and work it and down between the pointsRepeat entire cleaning procedure for second set of pointsdCheck points for good electrical contact, using ignition analyzer described under "Breaker Point Testing" Check and adjust breaker point setting described under "Breaker Point Adjustment