Looking for a heat exchanger core for this running D4400 marine CAT. Suspect the core may have a leak as I'm finding coolant in the raw water side of the system. Can a core be repaired? Does the entire heat exchanger have to removed from the front of the engine to get at the core?

Boat lives in Seattle, WA in the water. Engine vintage appear s to be around 1948 the year that the fishing troller was built.

Ned Johnson