A state or local law enforcement agency which has custody of a motorboat for investigatory purposes and has no further need to keep it in custody shall send a certified letter to each of the last-registered owners stating that the motorboat is in the custody of the law enforcement agency, that the motorboat is no longer needed for law enforcement purposes, and that after thirty days the agency will dispose of the motorboat. This section shall not apply to a motorboat subject to forfeiture under section 28-431. No storage fees shall be assessed against the registered owner of a motorboat held in custody for investigatory purposes under this section unless the registered owner or the person in possession of the motorboat when it is taken into custody is charged with a felony or misdemeanor related to the offense for which the law enforcement agency took the motorboat into custody. If a registered owner or the person in possession of the motorboat when it is taken into custody is charged with a felony or misdemeanor but is not convicted, the registered owner shall be entitled to a refund of the storage fees.