Leaking sinkmaster 850 garbage disposal

I ave a Sinkmaster 850 garbage disposal that leaks when the water faucet is turned on and draining into the disposal portion of the sink. The disposal does not have to be turned on to leak. The leak is at the bottom of the unit. How can I fix this leak? I guess I need a schematic of the unit to know what is causing the leak. I assume it may be an O ring seal part, not sure.

I do not see disposals on your list. I am choosing a category to allow this to submit.