Charlie,
It may be that water got you in this trouble in the fist place. If you make a new transformer, do it on a dry day!
Actually if it went shorted because of water (washing the chassis)it is most likely the HV winding in which case I'd say forget it. Find a replacement. I don't make my own automobile tires for the same reason. My time is too valuable versus what it costs.
You might be able to save it though. Pull the end bells and look see. Sometimes it shorts where the connections are and can be quite easily repaired.
Rob