My dealer has checked and cleaned all parts of the engine like impeller, heat exchanger and so on. He says its just condensing water. It does not smell like oil or diesel, but with the wind from the back there is a smell different from the exaust of my Yanmar engine of my trailer yacht. Sorry, i cannot find a correct discription, maybe like a „musty smell“. Could imagine it is the smell of burned coolant, the the level does not change really. But when I start the Volvo Penta, the level of the coolant in the tank goes dawn immediately.