You should have received the certificate of documentation when the sale was completed just like you would with a car title. You will need to send that in along with the proper form. They are sticklers for details, My boat had been owned jointly by a husband and wife but only the husband had signed the back of the certificate and the Coasties would not accept it. Wound up taking about 6 months to get the new certificate in hand. Part of this was due to going back and forth with an out of town seller and part was simply because sometimes there are pretty long wait times for certificate transfers.