351w carb version swap to whole new fuel injected motor

Will there be much trouble?I have every thing off the marine motor to swap. The truck motors were what they used. So why not? In a car the carb doesn't use the same fuel pump and the computer operates the tranny. So what about in a boat?

Well, for one, make sure the fuel injection was open loop, IE Uses a MAP instead of a MAF and had no oxygen sensor.

Also, the boat engines has slight advance in the cam which gives them more torque and less high end...

Then you need the shift assist circuit to help shifting if you have a dog0clutch Cobra outdrive...

I would never go from a carb to an old OMC efi system . Search function will lead you to threads where people are desperately seeking parts. The ECU has a truck part number but some weird flash file in it as I recall. I remember advising ripping the injection off, buying a manifold and carb.
It's a boat - keep it simple and mechanical.

In addition to what hystat mentioned, Marine engine loads are different from that of automotive, therefor the fuel metering is not quite the same and may cause issues.

If the auto injection system computer controls the ignition advance, this may cause issues as well.
(Marine engine ignition advance curves are somewhat conservative over that of automotive)


.

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.