I think that's a risky connection. As noted earlier, you're going to have to get from Terminal B to Terminal E. Since it sounds like you are set to fly on a day on which CO is running both CO #1696 and CO #1642, if you or your bags misconnect, there is a back-up, subject, of course, to space being available. Based upon my experience on this route, these flights are rarely full, so you'll probably be okay. So long as you plan your diving (you must be diving, right?) to account for the later arrival, the question you should ask yourself is whether saving $150 is worth a potential four-hour layover at IAH and the slight risk that CO #1642 will be packed to the gills.

On my last trip to CZM, I made my connection to CO #1696, but my bag did not. CO got it on CO #1642 and it was delivered to my hotel in plenty of time for me to have my gear for my twilight/night dive that evening.

When's you trip? If it's far enough out, it's possible that a schedule change will solve your problem (either by giving you more breathing room on the connection time or by shortening it and allowing you a change to a tidier connection to CO #1642 at no cost to you).