I know there is a drain plug on the bottom of the case, but where is the oil tank drain plug? its a 83SC

On the bottom of the oil tank

ok

Be sure to have a *really* big drain pan... Or you'll be in for a suprise.

And make sure that you have a very large hole for it to go into. The nice "enclosed" ones with a small hole for the oil to drain, even though they will hold the oil, do not drain fast enough.

I bought a 10 qt with the large lid, maybe 6-7 inches in diameter, and drain it into that.

James