Boat from Ambrym to Malekula or Vis-a-versa

Does anyone know if there are any scheduled boats from Ambrym to Malekula or Vis-a-versa, other than the two private boats that are mentioned in Lonely Planet Guide that costs 10,000 vatu one way?
Thanks

Most boats visit Malekula OR Ambrym on their way from Vila to Santo. Few if any visit both, making crossing beteen them by public transport tricky.

Thank you. I guess I will go to either Ambrym or Melekula, then by boat up to Santo, then catch the other boat back down to the other one. Seems like the only way as I do have plenty of time and not so much $$.