NCI received call from yacht Cherie aground in estuary off Topsham, reporting 2 POB, engine overheating, no VHF radio, no immediate danger. Rising tide, would call back if assistance required. Solent CG advised. Further call from yacht advising firmly stuck on sandbank and assistance required. CG would contact direct. ILB launched to assist and offer safety advice as yacht had run aground for the third time today. ILB towed yacht off sandbank and back to Topsham.