The escape of Mercury fom the stable spin-orbit resonance in which the spin angular velocity is twice the orbital mean motion (2n) requires that the kinematic viscosity of a molten core with a laminar boundary layer be comparable to that of water (0.01 cm2/s) and that tidal Q≲100. If the boundary layer is turbulent, escape from the resonance is only consistent with a liquid core of low viscosity if the critical Reynolds number for the onset of turbulence is >500, the moment difference (B-A)/C≲10-5, and the tidal dissipation factor Q≲40. These conclusions depend on the assumptions that Mercury's obliquity was near 0¿ at the time of resonance passage, that the liquid core was not stably stratified at the time at which Mercury passed through the resonance, that a turbulent boundary layer can be characterized by turbulent or eddy viscosity coefficient, and that the most important coupling between core and mantle is a viscous coupling at a smooth spherical boundary. Any additional core-mantle coupling would make it unlikely that Mercury could have passed through the 2n resonance with a liquid core of low viscosity.