SET OF 8 PERFORMANCE SPARK PLUG MERCRUISER&nbsp;8.1L MAG (all) Inboard 8-cylinder GM Big Block AWK408GR15ZC282ht 1. Higher HP and torque by up to 3 % 2. increased economy by up to 5% 3. 360 Firing Technology 4. Improved acceleration by up to 15 % 5. 5 UP TO 600 HOUR LIFESPAN