Instead of outdated coastal radars Iran can build something similar to the anti air EO-IIR complex to detect surface vessels. Ships have a large infrared signature and move slow. A much smaller(so more mobile) imaging infrared system would be able to detect ships. A laser or a radar range finder can get the distance info.
Another mistake is installing those long rane large radars and thinking the area is secured and forgetting about them. It is very easy to destroy radars once they are located and it is easy to locate them. The bigger the radars the more difficult to move them and reinstall.
Any air defense asset has to be moved every hour and re installed in another location. Even smaller EO-IIR systems need to be moved every hour because satellite pictures can show their position. Otherwise it is normal that they will be detected and destroyed. Remaining static targets like radars around Hurmuz would possibly be targeted tonight if they are not moved elsewhere.