rowley,
Being as all 3 Engineering Managers report to the President, the President is responsible for Engineering.
Co-ownership is problematic in many organizations. It means no one is really in charge of that part of the system.
One way to solve this is to dig into the differences. For example, you may find one manager is responsible for hardware engineering, another is responsible for software engineering and the third is responsible for process engineering.
Good luck,
John