Thanks for the reply. It does make sense that a significant amount of the testing would be performed with an electric system because of the convenience. I have two Astroflight brushed marine 25s installed in a Dumas 48 inch PT boat. The motors are counter rotating and each one is run separately by an Astroflight 408D reversible speed control and its own 14 cell nickel cadmium battery pack. They are turning at about 8000RPM according to my calculation. The controls are connected in parallel to the throttle channel. They are not necessarily synched as each motor and controller are slightly different. When they get out of synch, the boat runs tilted to one side and digs in on the same side during a turn. I’ve uploaded a couple of images to show you the installation. From what I have read, the Twinsync should help. Do you see any problem with the counter rotation?

Dan Reiss