The distributor distributes the high voltage spark from the coil to the correct cylinder required. Eventually they wear out over time like the spark plugs and wires resulting to poor electrical insulation which causes engine problems in the future therefore making it important to be part of the regular tune-up maintenance. Only works with HEI (High Energy Ignition) Systems and will not work with Point Ignition Systems. This replacement ignition coil by AA Ignition made by an original equipment supplier will get your 5.0L, 5.7L, 6.2L, 7.4L & 8.2L Mercruiser GM petrol engines with Thunderbolt 4 and 5 ignition systems.