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ICM question

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Bourget

New member
Greetings, just a quick question about ICM for 1995 454 xli TBI. Are Marina parts stores just using a regular ICM for automobiles? I have read that marine use ICM may have been programmed different then auto and mixed feeling from the internet about this. I did buy a GM branded one from auto store and used it to test the boat having issues and it ran good as far as I can tell. I had one sent to me for double the price from a well known marine store and I think it’s the same, I will compare numbers on them when I uninstall it from the boat. It’s a couple of hours away so maybe next week. Thanks for any insight
 
Here are my thoughts on this topic....all assuming you are referring to the ICM inside the Delco Voyager EST distributors...

If you have an ECU that explicitly control the timing advance, it really doesn't matter who's ICM you use as it pretty much just functions as a switch.

If you don't have an ECU then the timing advance used is the one 'built into' the ICM...Looking at the limited OEM data available, most factory configurations using the EST have what i call "very steep" timing advance curves. They are far from optimal but do provide 'factory approval'. Most all of the EST ICMs sold today are aftermarket. and most of those were originally developed for the auto applications...The original Delco service parts came in a handful of version but those part numbers are no longer available (except for NOS stashes). The factory branded parts I've seen in recent years are all aftermarket.

Bottom line - I don't think the premium for the 'marine branded' auto part is worth that cost.
 
Mako, Thank you very much for replying and summing up this topic for me! Hope this will help others on the topic. Your knowledge and insight is greatly appreciated!
 
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