Mercury thunderbolt

Need some advice lads ,I've a 1980 40hp mercury with thunderbolt ignition,I'd like to change an ignition coil has anyone got some spare that work ,I seen new ones in marine parts direct in swords but I'm not sure if they would be compatable they look the same but I'm not sure if they would be rated the same ,any help would be appreciated before I fork out for two new ones

Try OB Marine, I got one there for my 1974 Mercury blue band