boat standalone ecu pcm

Can the stock car computer be used to run the 3.5L 'standalone'? I'm looking for a very lightweight engine to put in my 16ft jetboat. I have a 3.4L SHO v8, but can't get the computer to run it. Don't want to buy any aftermarket ecu's. this is a $1,000 boat project, and I have $300 left in my...