For your sailboat, you need a computer. FB can't do anything without it (well, it can, but nothing usefull). I believe there is an add-on project in the subforum that might meet your needs. Otherwise you should look at some of the other options (arduino, raspberry pi + FB could be interesting). From your post, I'm not sure you understand that the brain is only an INTERFACE between the computer & the inputs/outputs, it has no logic/memory onboard. it converts analog data to digital & passes to USB & vice-versa, everything else is handled in software on the computer.
MDX is no longer being developed. I believe that FuseGL will work with the V3/V4 (i think I remember reading that, I'm going to test as soon as I get some time, which might be never...). It's still in beta, so I don't think its linked on the website yet. It's available from a link in this forum.
There is code floating about to control a V3/V4 via VB.net that I could send you if you give me your email address. It was written by MX270a, but he's no longer active here. It wouldn't be hard to move it over to C or C#.