The overlapping resonance regime is studied from a temporal viewpoint for a model vibrational predissociation in the framework of the Feshbach partitioning method. The memory kernels that are related by Fourier transformation to the energy dependent effective Hamiltonians are computed by wave packet propagation. The characteristic time tau(memory) of the memory kernel is compared with the time scale of the dynamics in the bound subspace. An approximate expression for tau(memory) is derived. tau(memory) depends on the bound-free couplings on a wide energy range. It is shown that the nonoscillatory shape of these couplings as a function of the dissociation energy is a typical feature of the vibrational predissociation.