hey fishey
when i read your post i figured thats what you were thinkng because i know you know your stuff from reading your other posts .:prayer:
as you said if all the oil was going through the cooler then i would want BIG lines on there.
do you need an oil cooler on the street engine well no we all proved that .
does it make an engine last longer under severe duty operations YES .
a marine engine will last about 8000hrs longer with an oil cooler than without one .