That is the chart off of the back of the Evinrude price book. When Evinrude went from sand cast iron to die cast Aluminum, the reports of stripped spark plug threads began the show up. At that time the instruction book said to screw in your new plug hand tight and give it another quarter turn to seat the NEW copper gasket. Obviously many were doing that with an OLD gasket. After a service bulletin giving an installation torque of 20 foot pounds didn’t eliminate the problem, they changed the casting die to use the H-10 spark plug which has a half inch of threads as apposed to the J series which has only 3/8″ – The J7-C may be used if you are careful not to over tighten – 17.5 to 18 ft. lb. . .
