Thunderbird 4 ignition system - replacement - GM 454 CI 7.4L

[LyndonGraves]

Has anyone been able to remove the Thunderbird 4 ignition system?? I have a 1988 230 Weekender with 7.4L mercruiser (GM). I believe the ICM is bad, and I cannot find a new one online. It has been suggested that I swap for a Holley MSD distributor. Another mechanic states that this will not work because there is a micro shift delay shifting. He said the motor will die or lug down. Does anyone have any experience or suggestions? Thanks!

 

[Thornton69]

Have you looked at the Delco EST (Voyager) marine ignition systems? Will likely go that route myself if the thunderbolt system fails in mine.
Haven't personally tried one in front of a prop, but have had them in a couple different jet boats and they worked great.