He will need to go to TPWD's website and towards the bottom he will see:
Abandoned Boat and/or Outboard Motor Request for Bonded Title Review
This form is used to request a bonded title review for an abandoned boat and/or outboard motor left on private property without the consent of the property owner for more than seven (7) days. The request will be reviewed and if approved, a packet will be mailed to the applicant containing information and additional form letters to use for sending notice to the proper law enforcement agency and the owner(s) and lien holder(s).
If approved, a public notice will be posted on the TPWD website for a period of six (6) months to allow owners to claim the asset. If, after the six (6) month web posting, the assets are not picked up by the legal owner, lien holder, or law enforcement agency and there are no legal claims of ownership, applicants will qualify for a bonded title.
If the situation does not qualify, then a response will be mailed back to the applicant stating the reason for denial.