Question about exhaust system blockage

Frank Langer

1984 Ericson 30+, Nanaimo, BC
I have not removed any part of the exhaust system in 16 years (eg, riser, muffler, etc), but I get good strong exhaust water at the transom. If parts of the exhaust are getting carbon deposits, would I still have strong exhaust water flow? I don't want to dismantle parts, especially these, unnecessarily.
Thanks for any opinions.

Kenneth K

1985 32-3, Puget Sound
Blogs Author
If you have a vented-loop Tee-fitting in your raw water line, water (that would normally be pumped through the injection elbow) can be pumped out through the loop vent instead. If, like my vent, yours is plumbed back into the exhaust hose at the through-hull fitting, you can't differentiate between actual "exhaust" cooling water and "vented" water as it exits the through-hull. Other boats apparently have a vent line that exits separately from the main exhaust hose.

"Carbon deposits" implies sediment build-up in exhaust-gas-handling components--valves, manifold, riser, hoses. None of these should affect water flow as the engine likely wouldn't run if the exhaust airflow passages were that restricted.

Intake obstructions, faulty hoses, clogged heat exchangers, and "mineral deposits" are the usual culprits for cooling water restrictions. Mineral deposits are most common at the fitting where water is injected back into the exhaust.

My surveyor commented on "exhaust steaming" during my sea trial. When I removed my water injection elbow, it was 80% blocked. Exhaust water flow was much higher after replacement.

Clogged elbow.jpg