Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 167Get this manual
TROUBLESHOOTING Spark Plugs 1- Check the plug wires to be sure they are properly connectedCheck the entire length of the wires from the plugs to the magneto under the armature plateIf the wire is to be removed from the spark plug, ALWAYS use pulling and twisting motion as precaution against damaging the connection2- Attempt to remove the spark plugs by handThis is rough test to determine if the plug is tightened properlyYou should not be able to remove the plug without using the proper socket size toolRemove the spark plugs and keep them in orderExamine each plug and evaluate its condition as descr ibed in Section 5-2If the spark plugs have been removed and the problem cannot be determined, but the plug appears to be in satisfactory condition, electrodes, et then replace the plugs in the spark plug openingsA conclusive spark plug test should always been performed with the spark plugs installedA plug may indicate satisfactory spark when it is removed and tested, but under compression condition may failAn example would be the possibility of person being able to jump given distance on the ground, but if strong wind is blowing, his distance may be reduced by halfThe same is true with the spark plugUnder good compression in the cylinder, the spark may be too weak to ignite the fuel properlyTherefore, to test the spark plug under compression, replace it in the engine and tighten it to the proper torque valueAnother reason for testing for spark with the