Nice idea saddled unfortunately, with incomplete planning.
1) I give those exhaust weldments about 5-6 hours worth of OM617.952 vibration before they develop a crack about where they're welded to the turbo outlets. If there was anyplace on a boat where you need a flexible coupling, it would be at that turbo outlet (think about what that engine does to aircleaner mounts).
2) That boat has two different engines. The portside engine has an SLS pump. Doing a project like this, I believe that I'd find two IDENTICAL engines to work with.
3) The soft, squishy high-dollar, over-engineered MBZ engine mounts have been left out enitrely. I can just imagine what kind of vibration those engines will transmit into the hull of that vessel at idle.
4) OM617.952s are ungoverned above 1100 rpm. It will take CONSTANT throttle jockying to maintain a given speed especially during low speed manuvering while docking
Mind you, the fabrication skills shown in that album are amazing. I'm soooo envious of someone that can pull off that sort of stuff.