You might look into Mini-ITX. Its the size and power consumption of a laptop,
but with pci slots and replaceable disk drives, etc. Of course, not that much
bang for the buck, compared to off the shelf stuff.

Do you mean small form factor computers like this
Shuttle?

Like one in link?

http://us.shuttle.com/SB81P.asp

If yes..... this is the model I was wondering COULD be
used for boating applications.