Thanks for the advice on the Barnacle Buster, Kevin. I finally got my gallon of concentrate yesterday and soaked the Hx for a few hours last night. That was some science experiment going on! Lots of bubbling and gunk evacuating the exchanger. After rinsing and running a stripped 12g copper wire through it, it seems like it is mostly cleared out. I am resoaking to see if I can get the wire to go through each inner cooling tube easily, but when filling with water, they all seem to drain properly now. My NEW Hx should be arriving today, so I will keep the old unit as a backup. I won't know if this completely solves my overheat problem until I re-commision the boat in a month or so, but it certainly was a major contributing factor.
My gut tells me that was the issue (fingers crossed), but if not, I'll figure it out! With a new Hx, new hoses, thermostat test and new fluid, things start to get more complicated. Thanks to everyone for the help.
Dave
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