Rattle gun undoes those bolts, I'm guessing this is the reason it was dumped. Might have to see if you can get stilsons or something like that to hold the boss. Have you got the mower tipped on its side, oil should not come out the exhaust like that unless you have it tipped on its side. Did you remove the petrol tank before tipping it over? Best way if you want to work on it is tip it up on the handles, that way the oil and fuel won't run out, otherwise remove the tank and drain the oil
