In recent years, the Internet of Things (IoT) has become the most innovative and efficient technology globally. IoT uses physical devices for establishing a real-time interconnection between heterogeneous networks. MANET plays an essential role in IoT-based systems for multi-hop data transmission, rapid setup, dynamic topology, etc. Generally, MANET is structureless and does not require any base station to achieve data transmission. In MANET, routing plays an important role, and modern IoT devices' evolution supports routing efficiency. MANET with IoT is applicable for various applications like emergency operations, disaster management, and environmental monitoring. Several mechanisms evolved to achieve secure routing on MANET with IoT. But still, achieving enhanced MANET performance with satisfying all QoS parameters is a challenge. Most of the existing systems lack a secured routing system, and there is no proper predefined mechanism for handling the packet losses. However, few approaches support multipath routing but fail to obtain the optimal power consumption. We use the routing manager-based secure rate analysis (RMBSRA) mechanism to address these issues. The proposed system is a centralized mechanism built with three major components: routing manager, neighboring table, and routing table. These components are responsible for effective packet transmission in the shortest path without data losses. The proposed system improves the multicast routing system by balancing the bandwidth allocation and eventually traffic on the network. The proposed RMBSRA performance is evaluated in the simulation environment NS-2. The observation obtained from RMBSRA is compared with the existing Trust-Based Secure Multipath Routing Protocol (TBSMR) and real-time secure route analysis (RSRA). The proposed RMBSRA achieves enhanced routing performance compared to the existing mechanisms.