Baseplate Magnetic 15 inches length. Please refer to the drawing below.
These baseplates do away with the nylon thumbscrews and use dual 150lb magnetic switches to hold the baseplate to a nickel plated steel plate. Ordering this mounting will substitute the magnetic sub plate in place of the normal aluminum sub plate.
These baseplates hold reliably up to about 4mph trolling speeds (assuming about 12 inches of downrod in the water).
They are available using marine board baseplates as their release upon hitting obstacles is much more refined than the breaking of a nylon Thumbscrew.