I do not know the model # of the engine, but thought it odd as well as this is something that comes up from time to time. I recall looking before calling the charter company and thinking this is almost impossible to get to as it was very tight in the engine compartment and I am a larger person. When I called them they told me it was behind the H2O pump and that they wanted their person to do it. I had no problem with their recommendation. Spare impellers were in the tool kit. Getting into Union on one engine in 30+ knots of wind is not something I would like to make a habit of. It was not pretty, but we got it done with minimum cursing.