Chrysler 100, 115 and 140 HP Outboard Motors Service Manual, OB 3439, Page 96Get this manual
SPARK PLUGS DescriptionA spark plug consists of two electrodes separated from each other by an air gapThe side electrode is connected to the shell of the spark plug The center electrode is completely insulated from the shellThe high voltageproduced in the secondary coi winding, is applied to the center electrode and causes spark to jump the gap to the side electrodeThis spark ignites the fuel-air mi xture and starts the combustion process in the cyl ind erThe gap between electrodes is critical because it affects the entire range of engine performance startingidlingacceleratingpower and top speedRemovalUse 13 16" deep well socket with rubber insert to protect spark plug insulation InspectionIn nearly every case of spark plug failurethe cause must be corrected before new spark plugs are installed Otherwiseservicing will be needed again in short timeEngine misfire or generally poor operation is often caused by spark plugs in poor condit ion or with improper gapThe first thing to do after removing spark plug is to carefully note its condition as this is