Oh man, guess I clicked the “buy it now” too soon! I just ordered one yesterday before starting this thread. Thanks for the offer though.

So to close the loop on this thread, I got the pump running again! I followed Merc’s TSB that I referenced above somewhat, but improvised a little. Instead of using fresh fuel and their stabilizer, I decided to be a bit more aggressive and used 50/50 kerosine and ATF. I pumped it through fuel line from the fuel/water separator filter outlet through the seized pump and back out to the inlet of the EFI fuel filter. I let it sit overnight and tried hitting it with battery voltage, still no go. It still just made a click sound like a solenoid being energized. I then made some jumper wires and hit it with an 18V cordless battery. Still the same click in the forward direction. I then reversed polarity for a moment and it freed up! I plugged the pump back in to the harness and cycled the key as normal and it’s been good to go since! I ran the boat today, burned about 40-50 gallons between both engines - they ran great! I’m chalking this up to ethanol fuel gumming over the winter.