Model towing tank testing is used to predict the powering required for full-scale vessels. Uncertainty analysis has up to this point focused on potential errors in the model data from the tests performed. The overall sensitivity of predicted power from this and other prediction methods to variations in inputs from the model tests and from elements such as the frictional resistance coefficient or correlation allowance needs to be determined. Rather than setting up a series of data reduction equations, a Monte Carlo simulation was used and the entire method was used as the data reduction equation in the uncertainty analysis. Several different extrapolation methods were studied to assess variation in powering prediction methods resulting from variation in input data and from the variation of the details of the extrapolation. Methods of reducing the uncertainty in the predicted power from the ITTC 1978 method were proposed. An analysis of model testing work on a geometrically similar series of podded propulsors follows the powering prediction work.