This paper addresses the search and track coordination problems of multiple shipboard radars. The proposed approach first exploits the physical characteristics of a single phased array radar to improve its effective capacity. Its effective capacity is abstracted by a closed-form equation called a schedulability envelope. Using the schedulability envelope for each radar, we deal with search and track coordination as a relative-load-balancing problem in a multi-resource environment. The simulation results show that the proposed approach significantly improves the overall capacity of a multi-ship multi-radar system.