Guys, I am in need of a used lower unit, I have found a couple of used engines that have good lower units. Here are the model numbers of what's out there S175TXRX, S150TXRX,(?)150TXRX,Z200TXRZ. Any ideas as to which of these will fit my C150TXRX? These are all 25 inch shaft models, the first X tells me that its 25". The S series is saltwater models. Thanks for the help guys!