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After rebuilding both engines, it was time to replace the factory Cummins exhaust elbows which otherwise are a ticking time bomb. This is because the wet elbows never fully drain the salt water out when the engines shut down. They will eventually rust through and create a salt fog effect which can destroy turbos, burn valves, score pistons etc. etc... and could ultimately destroy a very expensive engine.

The new exhausts are schedule 10 pipe and schedule 10 pipe elbows in 316 cres. 316 cres is one of the most corrosion resistant stainless steels. It is far superior to 304. The mixer components are also machined from 316 cres. The inlet and discharge are area matched to ensure the entire mixer fills with seawater. Ready built mixers are available from various manufacturers, but we made our own. Everything is TIG welded together with 316 filler rod.

Some crude jigs were made from angle iron and mig-welded together so that mockups could be made from cardboard before cutting the final components. The metal sections were tacked together using stainless wire in a mig welder. The units were then TIG welded together by a friend of mine.

The exhaust design uses a dry riser section that places the mixer downstream, in a gravity drain position. This enables all the salt water to drain out of the mixers when the engines are shut down, while preventing any water from sloshing back into the engines. I believe that ABYC code requires 6 inches of clearance between the dry section and any structure (f/g) in the boat. There are 2 rigid mounts on each exhaust which are isolated with rubber dampers.

The exhaust blankets were made locally by Orange County Thermal Industries. They needed the exhausts for about a week to complete the blankets. Turnaround was about 2 weeks.