Dongle Squares

So I'm repairing a flair hot tub... So far I've installed a new board and hooked up only the heater and the top side panel. The box needs to be updated I know that but, something odd happened where the heater immediately turned on and began over heating. I've never seen that before, is that normal? What could cause the heater to just turn on and run dry with a new board? Sensors being bad?

So I have a couple marathon pumps I'm trying to fix up... I have the correct impellers and they match the original. My issue is the shaft seal. I have ordered like 4 different variety of shaft seal and literally none of them fit this thing. I'm at a total loss, I've never experienced this before . Picture of impeller attached to post. Also impeller pn- 35-605-1000 CMP wet end 3.0 hp Basically the impeller shaft seal fits all the way up until the lip on the shaft where it expands out wider. Any ideas?

So I have a 2022 SX hot tub. Recently hurricane Ian really devastated the entire area and my hot tub was quite affected. I was able to restore the pump, clean the tub, fix the heater, and last thing is the board itself. I cleaned it super well, used so isopropyl alcohol to clean the dirty bits of it, there is definitely some rusting and stuff but I've definitely seen boards in way worse condition work before. My question ultimately is, is there anyway to troubleshoot the issues with the board? I'm running power to it, jumpers are properly configured, and I get absolutely nothing even showing it's trying to power up. I'm running 120v 20a, the GFCI doesn't trip it just stays on but nothing powers on the board. I have experience with soldering and testing with meters but not much. Is there anyone here with that kind of experience that could help me identify where the issue is originating from?