[bpy]

Not bad at all.   At least not that I notice and its less than if you have 2 or 3 outboards hanging off the transom.  If you have the engine hatch lifted slightly, you can really hear them........which tells me Tiara did a good job of reducing the noise from the engine room.    

Probably the most remarkable thing about the diesels is the little amount of exhaust you actually smell.   My engines run all day as well as the generator, a lot of times at idle while hovering over a fishing spot.   I have never had anyone complain about the smell of diesel exhaust with these engines.     Which is a far cry from the old Catapillar days.