I have a newly installed 350 in my 1989 20' maxum. Originally the boat had a 305. I used the same dist, ICM, coil (probably shouldn't have).


i need a new ICM. It is a Thunderbolt IV V8-22. This is the original ICM (for the 305). I heard that I need to go to a V8-22A (for the 350). Can anyone enlighten me? Also these are not very common, I want to stick with the TB IV, but will another one (i.e. V8-24) work?

Thanks in advance for the feedback

I think the ICM/engine relationship goes like this (at least this is what I've pieced together on the web). Of course I may be wrong.

305 - V8-22
350 - V8-22A
454 - V8-24

If this is the case do I need to replace my distributor and coil, or will any of these work on my 350 and current dist,coil? Thanks for the help.

I don't think the distributor or any ignition module or same wiring can tell what size (cubic inch) small block is under it. Unless there is something different on the new 350 with respect to engine harness, wiring, etc., there should not be a problem using the original ICM and coil. Did a new distributor come with the new 350, if thats the case there may be a distributor -ICM compatibility issue. Is the new engine a radically different fuel system from the original 305? Efi versus carburated?
The other ICM from a 350 marine application may be a better part but not really necessary if all else stayed the same.

What problem are you experiencing that leads you to believe you have ICM problem?

Best Regards,
Ray @ Raylar

there is nothing different with the 350, it is a carb engine just like the 305 was. I simply snatched the 305 out and installed a 350 long block. We kept the dist,coil and icm the same.

Thanks for the help

You can run the module you have with no problems. The V8-22 and 22A are very similar. Here is a chart. The first V8-22 listed on the chart is a V8-22A and the second is the regular V8-22.