100% OEM Mercruiser / Quicksilver (1997+ )Thunderbolt V: (8) AC-MR43LTS "LONG" tread...(see pic), Plug Wire Set 816761Q17, Distributor Cap 805759T1, & Rotor 13524T1 (Kit 805759Q3) (1982-1996)Thunderbolt IV: (8) AC-MR43T "SHORT" tread...(see pic), Plug Wire Set 816761Q17, Distributor Cap 805759T1, & Rotor 13524T1 (Kit 805759Q3) 100% OEM Mercruiser parts. Fits all Mercruiser Marine V8 engines Thunderbolt IV & V HEI ignition system (5.0L/305, 5.7L/350, 7.4L/454, 8.2L/502). Please select IV (1982-1996) "Short" tread spark plugs or V (1997+ ) "Long" tread... see pics. IV (1982-1996) Service kit: (8) OEM Spark Plug AC-MR43T "Short" tread...(see pic), Plug Wire Set 816761Q17, Distributor Cap Kit 805759Q3 (Distributor Cap 805759T1 / Rotor 13524T1) V (1997+) Service kit: (8) OEM Spark Plug AC-MR43LTS (816336) "Long" tread...(see pic), Plug Wire Set 816761Q17, Distributor Cap Kit 805759Q3 (Distributor Cap 805759T1 / Rotor 13524T1) OEM Distributor Cap & Rotor # 805759T1 / 13524T1 supersede parts: 80575903, 13524T1, 805759A5, 13524T-1, 80575973, 27-805760, 805759A-2, 13524A-5, 8057591, 8057590-3, 16457A-4, 13524A-1 OEM Spark Plug Wires # 816761Q17 supersede parts: 84-816608Q61, 84816761K17, 84-816761Q17, 84-813720A3, 84-813720Q4, 84-813720Q3, 84-816761Q4, 84-813720A4, 84-816761A4