Um, no. The Ford EFI is not only robust but very well capable of fueling a marine engine. If you use an ECU such as the A9L, you'll have absolutely no isssues running it in a boat. The only drawback is that the components on the truck version aren't "marinized", that is, made specially to avoid spark and/or sealed against moisture and salt water (distributor in particular). So from a safety standpoint I wouldn't drop a truck EFI in a boat. You don't want to hit the key and go boom.
That said, the carb is actually better suited to the job a marine engine has to do. Since boats are always "going up hill" so to speak, the carb offers fuel metering in a linear manner from idle to WOT. You don't really need the advantages that an EFI offers (such as better fuel economy in stop and go driving and adjusting for changes in elevation)
Besides, if gas saving is your thing you shouldn't be blowing it in a boat; one of if not the least fuel efficient mode of transportation outside of an Abrams tank.