Bill,
I just reread this thread. With all of the information here is what I would do if this was my boat.
- Remove the heat exchanger. Clean, pressure test, if good, repaint and reinstall (I did this on my boat the 2nd year I owned it as the PO never did on a 2001 boat). Replace the gaskets and o-rings. Oh, and the pencil zinc but you should be checking that monthly and replacing as needed.
- Remove thermostat and either replace or test to ensure it is good.
- Check the coolant pressure cap. Again I just replaced mine for the short money instead of checking it.
- Check all hoses. Look for leaks. Replace older hose preventatively. Replace or check all hose clamps (I only use awab style below the waterline)
- Recharge and rebleed the system with coolant. I used the Maine Sail technique with the ball valve and funnel (on the C34 wiki) but the other techniques listed on the C34 wiki will work as well.
I did all of the above as preventative maintenance. I would also add a coolant recovery tank if my engine didn't have one.
I would leave the coolant pump at the last thing I would touch. Unless you know it's bad, I would look at these other areas first.
One thing I didn't notice you listing at all was taking off the end caps of the heat exchanger and looking for debris that was obvious to see. Mine was filled with junks of zinc when I first took it apart. A gift from the PO.
Good luck and fair winds,
Jesse