Transporting boat from Canada back to us
 

I am looking at buying a boat from Canada, boat was from the U.S. Than sold to a guy in Canada
Will I have to pay a duty tax when I bring boat back into to U.S ?
Boat will be registered in MO

No duty tax. Just get a broker and pay a small bond. If your state has sales tax, you'll have to pay that.
I did this with the Cougar. Was a US boat, sold to a Canadian, and I bought it from the Canadian, I think the town was Sarnia.
I paid a customs broker something like 350 bucks to do the paperwork, but that was a while back.