The nonlinear mathematical model of the system to mount the motor in a niche of the outboard motor boat, which protects against external influences by means nonlinear shock absorbers and dampers, has been developed. The mathematical model of the system is represented by three nonlinear differential equations of second order. The nonlinear shock absorbers and dampers, as a function of the generalized coordinates are represented by polynomials up to the fifth degree inclusive. For approximate analytical solution of the nonlinear mathematical model is applied the modified method of polynomial transformations and the numerical method of Runge-Kutta.