I cut a garden hose reel leader in half and the outside diameter of the hose made a water tight fit with the inside diameter of the clear vinyl tube. It's good to be lucky sometimes.
Using the timer function of my iPhone, I clocked a minute and turned off the pump power switch when the alarm went off. It only took a couple of runs to get the PWM signal generator tuned just right.
Both the Seimens motor and the DMOC inverter call for 16 liters per minute, so this is a good result. At this speed, the pump makes no noise at all.
With both signal generators pre-set, installing the wiring for the cooling pumps will be a plug-and-go affair. I only hope all the other electric wiring goes as well.