Good afternoon.

I have a Minnkota Maxxuum 36 volt trolling motor. Old version. I am getting very little power to the prop. I have 12 volts at all 3 batteries, 36 volts at the plug where the foot control plugs into the console and I have 36 volts where the wires go into a sort of "control box" (sorry not sure what the correct name is) that is attached to bottom cover of the foot control. However on the other side of this "control box" I have very little voltage. Even with the trolling motor on high and on "run". I checked the voltage at the 2 leads that go down to the actual motor and they also are getting very low voltage ( like 1 or 2 volts). When I turn the trolling motor on it starts of very, very slow and then begins to get a bit faster but nothing like it should be. Is my problem this "control box" thing?

check the load voltage at the batteries when you put power to the trolling motor.

13.4 (or close to it) volts is what a battery should read (cold).

times 3 batteries 38-40.2 volts.

I would go one further and say that you should have someone use a meter to check the voltage of each individual battery as you press the RUN button for the trolling motor. The voltage on a bad battery can read fine until a load is applied. The voltage of a bad battery will typically plummet the instant a load is applied. By checking each of the 3 batteries with a load applied, a bad battery may be rather obvious.

If you don't see a largely different drop in voltage for one battery compared to the other two, you likely have a control board issue.

Awesome..... thank you very much!!!

I have to respectfully disagree, but perhaps you are thinking apples and I am thinking oranges.

13.4 is a typical voltage a battery will read when it is fully charged and the charger is still plugged in and in "float" mode and no load is being applied.

A charged battery at rest, given adequate time to stabilize after being disconnected from a charger or engine alternator should read between 12.5 and 12.9 volts, depending on condition.
Any applied load will drop the voltage from the resting voltage commensurate with the severity of the load.

as a past ASC for Minn Kota.
what i'm referring to is the LOAD pull on the batteries. the control board in the troller
has to have XX amount of voltage to operate properly, or it wont run or barely run. even if the
voltage shows good.
it's the loaded voltage that's important.

may or may not be the problem... but it's the cheapest and easiest place to start.