Originally Posted by In the red

Very easy nighthawk. Take the one bolt off each end and use a small screwdriver to pry the cap and gasket off. In mine the pieces (and a little lake grass) were in the water inlet end (port side of motor). I then ran a small piece of wire through the tubes in the exchanger to be sure and backflushed with a garden hose from the other end. Cleaned the gasket surfaces with a little sandpaper and put a new gasket and o-ring on. Did it on the boat. You can do it in 15-20 minutes