Matt, I agree with you the term "once and for all" is a relative term, but I like to think on the good side - that it will significantly improve what I have right now. Or at least I will have "fun" trying out something new and different. 13 years is a good "once and for all" for me at this point!!!
Scott, the motor I ordered is 22-48 volts, so will presumably require 24 volts input. I don't see a 12-volt version, but have not looked extensively.
I might be able to output 24 volts from the VESC controller, but I really need to get all these things and start experimenting.
If all else fails, I can simply convert to 24 volts at the pump interface in the blue box. I do that in other cases (both up and down) on the boat anyway. And yes, I have that same blue box now. Or I can use a simple relay, as you point out - easy to do with the 24-volt supply in the engine room.
Let me see what I can find out once I get delivery.
A54 Phantom #44