Hunter345,
You'll have to use some common sense and the formula of one life vest per passenger for boats over > 20 feet.
Federal law only requires single-hull boats less than 20 feet in length to have a capacity plate. Thus, in your case you'll have to follow the recommended capacity found in the owner's manual if it is even specified.
They do provide this basic formual below. But It is obviously designed for boats less than < 20 feet.:
Number of people =
vessel length (ft.) x vessel width (ft.)
15
Because using it on my Hunter 45 Legend, it says I could have up to 39 passengers on my boat. Which to say the least, is crazy by anyone's standards. I'd never take on more than a dozen without GOOD reason.
Regards,
James