If it helps, my Dufour 40 (2003), has an open ended 150mm flexible pipe hanging over the engine. It terminates at a grille under the helm position. This must be supply air.
Then I have a fan at the rear of the engine area, that runs when the engine is running. I assume to draw warm air from the engine compartment. This too, runs to a grille on the opposite of the helm position.
On the basis that Dufour wouldn’t run to the cost of installing all this without good reason, I surmise it is necessary.
With all the sound insulation in the engine compartment, is does get hot in there.
Good luck.
Bill Rawle