On the Catalina 30 MKIII, the exhaust swirls back into the cockpit and cabin. It stinks and leaves a mess all over the transom as well. The through hull is above the waterline with occasional dips below. Would moving the through hull below the waterline help? What, if any, modifications would be needed to prevent water intrusion?
Moving exhaust below waterline
- Thread starter Project_Mayhem
- Start date
Have you asked the fish how they feel about diesel exhaust in their home? 
The exhaust hose has to rise well above the waterline at any angle of heel. The length of the hose is also an issue. When the engine is shut down any water in the exhaust line before the high loop will drain back into the muffler and potentially into the exhaust elbow if the run is long and the exhaust line isn't cleared.
The exhaust hose has to rise well above the waterline at any angle of heel. The length of the hose is also an issue. When the engine is shut down any water in the exhaust line before the high loop will drain back into the muffler and potentially into the exhaust elbow if the run is long and the exhaust line isn't cleared.
Keeping the exhaust thruhull above the WL ensures that siphoning backwards when shut down cant happen. The gravity loop ( elbow ) won’t prevent that in all cases.