Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 169Get this manual
TROUBLESHOOTING Checking Compression 4- Remove the spark plug wiresALWAYS grasp the molded cap and pull it loose with twisting motion to prevent damage to the connectionRemove the spark plugs and keep them in ORDER by cylinder for evaluation laterGround the spark plug leads to the engine to render the ignition system inoperative while performing the compression checkInsert compression gauge into the No.1, top, spark plug openingCrank the engine with the starter, or pull on the starter cord, through at least 4- complete piston strokes with the throttle at the wideopen position, or until the highest possible reading is observed on the gaugeRecord the readingRepea the test and record the compression for each cylinderA variation between cylinders is far more important than the actual readingsA variation of more than psi between cylinders indicates the lower compression cylinder may be defectiveThe problem may be worn, broken, or sticking piston rings, scored pistons or worn cylindersThese problems may only be determined after the head has been removedRemoving the head on an outboard engine is not that big deal, and may save many hours of frustration and the cost of purchasing unnecessary parts to correct faul ty conditionCondenser In simple terms, condenser is composed of two sheets of tin or aluminum foil laid