Tacoma-based custom aluminum boat building company Silverback Marine has secured a multimillion-dollar Department of Defense contract for its new OX series truckable tractor tug, which is expected to be delivered in late 2025, the company announced Nov. 7. Silverback Marine teamed with Darley Defense, a family-run Illinois-based supplier of material support and training to the DoD, to win the contract. Designed collaboratively with Seattle-based Elliot Bay Design Group, the tug would feature two Cummins diesel motors, Schottel Z Drives and Arcosa deck equipment and winches, according to Silverback. “The core purpose of this mini tug is to bring real, useable…