Interesting, I recently noticed that less
cooling water came out of the
exhaust on my 40hp ISUZU inboard
engine.
After investigating I found that the reduction fitting from 38mm to 16mm, from the saltwater strainer to the
heat exchanger was nearly completely blocked by ablative antyfouling deposits ,which actually turned solid.
I never seen that before..live and learn.
Something else to keep an eye on.