Hydrofoil section data, comprising coefficients of lift and drag, are a key input into blade element momentum models of turbines. The aim of this paper is to investigate whether differences in this section data are to account for the predictions from blade element momentum models and Navier-Stokes solutions (using a computational fluid dynamics programme) disagreeing. To this end, a number of sources of hydrofoil section data were researched and compared. It was found that there were notable differences in the coefficients given by the data sets. Two of the data sets, namely the Sheldahl and Klimas data and results produced by the authors with Xfoil, were used as input into the blade element momentum model. When compared with the results from the CFD solution, there is disagreement between all of the results, although the results produced from the blade element momentum model with the Xfoil coefficient data are closer to the CFD results than those produced with the Sheldahl and Klimas data. This shows that whilst uncertainties in the section data may be partially responsible for the disagreement between the two models, other uncertainties must also be significant.