Never having worked on the
engine, I can't be sure, but from the drawing it appears that it can be removed from either end. A gentle tap with a block of
wood interspersed between HE and hammer should get it started out.
The real reason I posted is because of the picture you show, as compared to the drawing.
In your picture the exchanger appears twisted in the housing. This is a double pass exchanger, the sea
water goes in half of one end, traverses the length, reverses, and crosses back to exit the same end. If the exchanger isn't indexed to fit into the housing so the inlet and outlet sides are placed properly in respect to the inlet/outlet/separator plate, and alignment is off, the seawater flow through the unit will be impaired or nonexistent, and
cooling will suffer commensurately.
Just something to keep in mind, hopefully someone who has hands-on experience will come along...