Yep, going to need a LOT more info or some pix from several different angles.
Tin, fiberglass or wooden boat? Length?
You might get lucky looking thru the pix in the library
here and stumble on a boat that's similar.
Unfortunately, there are hundreds of boat makers that left little or no records behind for us to dig thru, so you might never ID it. Some only made 1 prototype and never built any boats for sale.
Look for a copy of Peter Hunn's book
Tail fins and Two-tones
It might have info that isn't online
It's also possible that a previous owner modified the boat
Lets see some pix of this finned mystery boat and good luck w/ your project