[olddog]

Did the boat have a closed loop anti-freeze system or did lake water circulate through the engines?

Did the boat ever run on salt water?

Does one engine rotate the opposite to other?

Boat engines can have a lot of rust in the cooling system and the cylinder walls may get too thin.

A lot of 427 FE boat engines look like they are a side oiler design, but they were not drilled and are center oilers.

I would say they are not worth as much as a car engine. I expect a lot of people would want to disassemble and inspect it before they would shell out much cash.