Jon
A while back you mentioned the need for three batteries to test these old thruster motors. Even though these are designed for 36 VDC nominal, it would be a perfectly good test and safer to connect to a single 12 VDC car battery. It would run at less RPM and determine if the motor is still good. The DC motor on my boat is designed for 120 VDC nominal. When I got the motor, I tested it with one of my 12 VDC batteries to confirm that is
was working and the rotation direction as a function of polarity.
Cliff