I change coolant every other year and remove the heat exchanger tube pack when I do, it’s six bolts and easy to do, means you replace two O-rings, so why not do it?
You could just pop off one end and clean the tubes and reinstall the cap a lot easier than jury rigging
up some kind of pump and bucket, hoses etc, and then where do you store these items for another year or two when you do it again?
I’ve not seen any significant scaling either.
I strongly suspect that pumping these solutions around work mostly because there isn’t much there to clean to begin with, and that they do cause some harm to the aluminum
bits in the engine.
I’ve briefly thought about putting in a T to my raw water line and flushing
the engine with it running with fresh water with the seacock closed, that would leave only fresh water in the engine when I’m just sitting, but haven’t done it because I’ve not see any corrosion
or scaling yet.
My engine is a 1987 model, so that makes it 33 years old, if it hasn’t rotted out or scaled up yet, it’s not likely to.