Hoping to get advice on whether to use fuel injection or a carburetor. I would be putting this in a 82 Challenger 21 a Mercruiser 350 5.7 bored .60 over. Any suggestions would be greatly appreciated.

$400 for an Edelbrock 750cfm marine carb, or $3000 for EFI

Well that answers that question, LOL. Thanks !!!

That and with a high HP engine no stalling as you pull up to a dock because you pulled it out of forward and put it into reverse. OH - that and never have to touch the throttle to start it.
I won't ever go back to a carb.

In daily life I am an EFI guy but
With a low hp small; block in a small light weight boat with a fast bottom...come on. LOL. Carburetor wins in a budget deal.

As far as fuel effeciency
People would crap their pants what even a 400hp 350 will do in fuel effeciency in a lightweight fast hull with a Holley style carb. hahahahahahahah

I 100% agree with you, but this is not what the OP is asking.

Carb all the way for this app. This hull ran 60mph with a Merc 260 in the early 80s.

On OEM STOCK marine fuel injected NON O 2 sensors and NON closed loop. You be surprised at the no to very little in fuel economy carb vs EFI produces. It barely none to small gains. And in a boat is there really fuel economy ? NO - some haul azz -- some ski all day --- some tube all day -- some wakeboard all day --- some load up their boat with way too much weight as well. Actually see this alot on holiday boating.. Fuel economy goes out the window in a boat.

Also I have from years ago Sea Ray produced fuel economy numbers carb vs EFI in their brand of boats - and believe it or not some carb apps got better fuel economy. I still have all the data to back up what I am saying here.

I would go with carb for the set up the OP is asking which way.