DON'T DO IT! unless you want to buy a new one....you might try what a friend did temporarily...he cleaned off all the paint and took it to bare metal, then made a "scab" patch with JB Weld...held for the season till he had a chance to have it welded professionally when he took it out and had it on the hard for the winter...Good Luck
Thanks for the replies. I did put some of that underwater epoxy stuff over the crack and it slowed the leak down to a slow drip. Should get me through this season. I'll keep an eye on the oil for signs of water contamination. I see no oil in the water, so I figure that's a good sign.
simpsoned, Do you happen to know what your friend paid for that and what the outcome was (ie did the weld hold up over time). Cast iron is a pain to weld correctly. I had been thinking of trying to find a used one to swap in this winter.