Seppäläinen and Valkó showed in [19] that for a suitable choice of parameters, the variance growth of the free energy of the stationary O'Connell-Yor polymer is governed by the exponent 2/3, characteristic of models in the KPZ universality class.We develop exact formulas based on Gaussian integration by parts to relate the cumulants of the free energy, log Z θ n,t , to expectations of products of quenched cumulants of the time of the first jump from the boundary into the system, s0. We then use these formulas to obtain estimates for the k-th central moment of log Z θ n,t as well as the k-th annealed moment of s0 for k > 2, with nearly optimal exponents (1/3)k + ǫ and (2/3)k + ǫ, respectively.