Thanks to both of you for your input but,....I have replaced heat
exchangers on both engines last year. They both are fine. The water
on the raw water side is more than adequate at all rpm. Placing a 5
gallon bucket under the exhaust at 2000 rpm will fill the bucket in
less than 2 seconds....these are 6 inch exhaust ports.

JPZ
(Surffb) wrote in message ...
Mineral/salt build-up in raw water side is likely. Inspect heat exchanger and
boil out as needed.
Fred