I bought a boat with a pair of Demon carbs on it, how do I know or can I tell what cfm they are?....Fred

I'd call Demon and ask them.
There has to be serial or part numbers on it somewhere.
I'm sure their tech reps would be glad to help.

I should've done this in the first place, here's a link to Demon's site on how to tell what carb it is.

Demon Carbs

I did call Barry Grany and the rep said to look at the number next to the secondary vent tube and call him back, I'm calling him back today with that info....Fred