Interesting, thank you. I don`t have the direct experience you seek, but have been looking online at a boat with 300hp D4s, and wondered about any issues. In discussion, my mechanic raised issues about end caps, O rings, etc, but generally, not in a D4 context. I hope Volvo reconsiders. Consumer law may take you beyond the manufacturers idea of guarantee/warranty.
Island Gypsy 36 Europa "Doriana"