Yeah, well add to the fact that you have an older marine clarion unit with C-Bus connectors and you are in my own personal hell.
So if I want to change my head unit, I will also have to change out the older remote along with the 6 CD changer.
I would much rather use the automotive units like you did because the Clarion Marine units are not all that feature-rich but the wired remotes will not work unless you plan on hacking the deck somehow.
If you are intent on using that unit, you might want to look into making an Infared repeater and use the handheld remote that came with it.
I think if you search on this board you can find a few people that have done it.