Check your oil. If it looks like chocolate milk you have a more serious problem, water in the oil.
If it is external only and just dripping water into the bilge you may be able to patch it up. A friend of mine with an LTR had the exact same thing happen, it only cracked externally (i.e. no water in the oil), he patched it with JB Weld and now removes the petcocks at the end of the year. Those petcocks are notorious for getting clogged with junk, you are better off taking them out at the end of the season.
Some people who are a bit more engine savvy should be along with more helpful advice but that should at least narrow down how serious your problem is.
94 Prostar 190, LT-1, Powerslot [SOLD]