Exhaust system

The exhaust system on Ocean Dove has been a challenge. The original exhaust system on the Volvo was a dry stack made of heavy steel pipe with 12" loop before water injection point that was bolted directly to the Volvo exhaust manifold. The new Vetus engine exhaust manifold could not support the piping loads or vibration of a dry stack bolted directly to it. For this reason I went with a complete wet exhaust system. The wet exhaust system should help keep the engine room cooler.
The Vetus engine exhaust injection elbow is on the stbd side, and there is very little room to install or bend a 3" exhaust hose. My original plan was to make a right angle after the engine exhaust injection elbow and go across the top of the gear box to the Vetus water lock muffler on the port side then up and over to reconnect with the old exhaust hose.
The exhaust hose run to the waterlock muffler must be lower then the exhaust injection elbow to prevent water flowing back into the exhaust manifold and engine. After I had all the exhaust system parts (hose, muffler and 90 elbow) aboard it became clear that there was not enough clearance for the 3" exhaust hose to go over the gearbox without creating a large hump in the exhaust hose that was well above the exhaust manifold.
I went back to the drawing board and came up with the solution under the engine.
To accommodate the new Vetus engine the fwd engine mounts had to be raised almost 6" above the original Volvo mounts, creating a large open area under the engine. This allowed me to install a fiberglass 90-degree elbow after the exhaust injection elbow and run the 3" exhaust hose fwd and under the engine to the port side then back aft in a large U to the water lock muffler.
I wanted the waterlock muffler as low as possible so I cut the platform on the port side to accommodate the lowering of the muffler and connection of the 3" exhaust hose. The outlets from the water lock muffler goes strait up and over to the port side were it reconnects with the original exhaust hose that runs down to the stern of the vessel.
The original owner had a 2" gate valve installed at the top of the loop that was accessible from the port lock in the cockpit. I removed it as I do not like gate valves and the 2" valve added a restriction to the system (I may install an 3" valve at a later date). The top of the loop is about 3' above the water line and there is about 2.5' down hill run to the exhaust outlet on the stern of Ocean Dove. All exhaust hose connections were double clamped "T" S.S. band clamps.

I was concern about the volume of water that could be in the outlet hose from the muffler to the top of the loop when the engine stopped.
The length of this hose is 76mm (3") X 183cm (6') with a total volume of 8.3 liters (2.2 us gals).
Volume in NLP75 waterlock muffler is 10 liters combined with the volume in the length of hose between waterlock muffler and engine exhaust injection elbow 76mm (3") X 183cm (6') of 8.3 liters totaling 18.3 liters (4.8 us gals) should be more then enough volume to accommodate any water that maybe in the outlet hose from the muffler.