It is my understanding that Jeanneau have switched from the well proven Nanni engines to the relatively new 4BY series Yanmar power units. The MF 705 has a single 4BY 150hp unit and the MF 925 has twin 4BY 150hp units. With regard to spares, J.S. Barruss are the Yanmar UK distributor who supply all the various Jeanneau and Benetteau dealerships.
I have a 4BY unit in my boat but when I recently approached Barruss for price and delivery for a Yanmar fuel filter I was told they were out of stock and directed to Frenchmarine who were also out of stock. Good luck!!!!