Hope this helps, from the TPWD.
Titles and Registration
Texas Registration Requirements
The following vessels when on Texas public water are required to have current registration, including when docked, moored, or stored.
•All motorized boats, regardless of length;
•All sailboats 14 feet in length or longer or any sailboat with an auxiliary engine(s); and
•USCG Documented vessels (New — see section below).
Exempted vessels — All (non-motorized) canoes, kayaks, punts, rowboats, or rubber rafts (regardless of length) when paddled, poled, or oared and sailboats under 14 feet in length when windblown.