Mercruiser 7.4 Liter Thunderbolt Tune Up Kit | M74TBOLT Mercruiser 7.4 Liter Thunderbolt Tune Up Kit M74TBOLT Comprehensive kit includes everything needed to tune-up Pre Vortec Mercruiser 7.4L engines with Thunderbolt electronic distributors. Normal annual maintenance items including distributor cap, rotor, spark plugs, spark plug wires, oil filter, fuel filter and fuel treatment For Mercruiser 7.4 liter 454 cu. in. GM V8 engine models using Thunderbolt ignition and NGK BR6FS spark plugs Packaged conveniently in one easy part number to order Just add the recommended engine oil