Listed here is a USED Mercruiser 8.1 Big Block Ignition Coil.  These are all Genuine OEM MerCruiser Mercury parts NOT cheap Chinese aftermarket replacements.  ORDER IS FOR ONE SINGLE COIL NOT ALL 4.  The part number for this coil is 392-881732 which supersedes to part # 300-8M0187403 and lists for $283.49 new from the dealer.  Ignition coil has some scuffing, pitting, wear, staining, etc. consistent with a part of its age.  All coils are fully operational.  These will also most likely work on Indmar, PCM, Crusader, Pleasure Craft Marine, as well as others.  I cannot cross reference most of these so please check your part numbers for compatibility.  The number 12558948 are stamped onto all coils and the number 108C28-0200 is stamped on two and the nuber 05C02-0200 is stamped into the other two .  This coil was most manufactured by Denso and their name is cast into the plastic.  This is the coil that is mounted to the top of the rocker cover on many 8.1L big block platforms through the 2000s.  May be used on other engine platforms and configurations as well.  These came from a 2003 8.1 H.O.  Mercruiser with Bravo setup that was used its entire life on a Orlando freshwater lake and has most likely never seen salt water.  Engine had around 375 hours when it blew.  NOTE: Mercruiser did use another style coil on some engines that look differently than this.  Please make sure yours looks like the one pictured since I am NOT sure if the other style is compatible with these.  Possibly fits on many Chevrolet, GMC, Chevy, etc. trucks as well but have no way to confirm this.  Coils are stored in a climate controlled parts room to prevent deterioration. If you have any questions or need help with compatibility please fee free to contact me before purchasing and I will help you to the best of my abilities.  Thank you for your interest.  Steve MMSLLC :)