This sounds like a hardwired safety bypass. Most likely. If it’s always done this then I’d assume there’s a safety disconnect switch that kills your ulterra when your outboard is on. To prevent you from blasting off without your troller stowed and breaking it. I’ve seen them before. It’s a safety bypass. It’s always better to install an isolator kit to allow your batteries to charge while motors running. After the starting battery has reached fill charge it will switch over to charge other onboard batteries. That and a good minnkota or Noco 3 bank onboard charging system would eliminate a lot of headache when it comes to safety bypass redundancy’s. They are a pain. But If this is something that’s recently just now started doing, then you may have some sort of relay issue. If the trolling motor has its own batteries it will either work or not work. It won’t drop and then start again after using the motor. If it’s too low amperage and voltage it will Simply not work anymore. I’d trace your main power wires from the trolling motor to see if they run to some type of enclosed switching rely housing. That alone would tell you a lot. It could be just a safety feature. Or you could have a relay shorting. But you need to trace the trollers power wires to see what’s between the battery and trolling motor. If you find an enclosed relay box that your trolling motors power leads to, along with some smaller wires, I’d try finding a product name and number on the junction box and find the installation specs so you can remove it and just put in a manual battery bank switch that you can manually use. If there’s already one on it then I’d bypass any possible junction. But don’t just go ripping out wires. Do your homework. Ulterras are spendy so identify, find literature/installation specs, and simplify unnecessary fail safes. And that is only if this is something that’s always been this way. If it worked differently before, I’d still start by tracing the power wires to see what all lays between the troller and batteries. Identify, research, diagnose and simplify. Hope this helps
