A method for fast numerical simulation of nonlinear wave propagation based on a quasi-linear approximation has previously been presented. In the current study this method has been further developed to yield correct levels of the secondharmonic wave. The method can be used for 3D simulations of second-harmonic fields from arbitrarily transducer geometries. The method has been validated by comparing simulations to results produced by a conventional nonlinear simulation model and to experimental measurements. The reference simulation model was a numerical solution of the KZK equation for a forward-propagating pulse using a operator splitting approach. Experimental verifications were performed with hydrophone measurements in a water tank. Results showed a good match between the simulation models and measurements for MI up to 0.4 for an annular array probe and for MI up to 1 for a rectangular probe. For higher MI values the quasi-linear method showed a gradual increased over-estimation of the second harmonic field.