100% OEM Mercruiser / Quicksilver (1996+ )Thunderbolt V: (6) AC-MR43LTS "LONG" tread...(see pic), Plug Wire Set 816761Q16, 815407Q5 (Distributor Cap 815407A2 / Rotor 13524A6) (1985-1996)Thunderbolt IV: (6) AC-MR43T "SHORT" tread...(see pic), Plug Wire Set 816761Q16, 815407Q5 (Distributor Cap 815407A2 / Rotor 13524A6) 100% OEM Mercruiser parts. Fits Mercruiser 4.3L V6 engines Thunderbolt IV, V, and HEI ignition system 4.3 L 262 CID Please select IV (1982-1996) "Short" tread spark plugs or V (1997+ ) "Long" tread... see pics. IV (1985-1996) Service kit: (8) OEM Spark Plug AC-MR43T "Short" tread...(see pic), Plug Wire Set 816761Q16, Distributor Cap Kit 815407Q5 (Distributor Cap 815407A2 / Rotor 13524A6) V (1996+) Service kit: (6) OEM Spark Plug AC-MR43LTS (816336) "Long" tread...(see pic), Plug Wire Set 816761Q16, Distributor Cap Kit 815407Q5 (Distributor Cap 815407A2 / Rotor 13524A6) OEM Distributor Cap & Rotor Kit # 815407Q5 (Distributor Cap 815407A2 / Rotor 13524A6) supersede parts: 815407Q02, 815407A2, 18-5274, OEM Spark Plug Wires # 816761Q16 supersede parts: 84-816761Q16, 84-813720A11, 503751, 18-8810-1