My boat has 2 batteries. One house, one starting. The starting battery is larger than the house battery. I can’t tell you the exact sizes of them right now. But they are hooked up to a Marinco Parallel battery switch. Here’s where it gets confusing. The switch has 1, 1&2, parallel, and off switch options. Not like your regular perko battery switch. Position 1 does nothing but turn on the mercury VesselView. Postion 1&2 runs all the systems, but only one battery(starting) is charging during this process. Position 3 “parallel” using all systems and charges both batteries. After Using 1&2 all day, my power steering, trim tabs and jackplate all stopped working due to low voltage. So after fully charging all batteries and running only on parallel setting, I’ve had zero issues. Parallel is supposed to pull power from the other battery to start the motor in a dead battery situation, seems odd that I need to run it in this setting at all times in order for everything to work. There is also a DVSR (digital voltage sensing relay) in the wiring schematics that is supposed to decide which battery to charge due to voltage demand?? Also there may be 2 inline fuses, one for each battery cable that I haven’t been able to locate yet. I’ve spoke to the dealer, and the manufacturer and they both said they didn’t wire this thing up and blamed it on each other. Not a common switch and I’m trying to figure it out and prevent further voltage problems without having to running it on parallel at all times. Would be much easier to have a 1, 2, 1&2, and off setting switch and control which battery I use for all functions. I’m also wondering if the power steering, jackplate, and trim tabs should even be hooked up to the house battery… bc the motor starts off of the other battery. Could this be the main issue here? Included below is the switch itself, and the wiring schematic that is supposed to be with this switch on a single engine dual battery application. I have checked all settings with a multimeter while the boat is in idle at the ramp to verify which batteries are actually charging and when.