How viscous is the oil? Thin like motor oil or thick like gear oil? Often engine and gearcase oil have a very different smell so you can give it the sniff test.

Only you can see where the oil is coming from. If dirt is preventing you from seeing the source I'd hose all the under bits off with engine degreaser and hose it off. Once everything is clean hopefully you can track the oil back to it's source.

 

It is thin like motor oil. I’ve hosed the whole area off to try and locate the source but can not pin point it. It seems as though it is coming from the bottom of the engine but can see oil sitting there in the housing.

 

There are 2 sources of oil, the engine and the hydraulics. I am not familiar with your mower arrangement but assume they are in close proximity making identifying the source of the leak difficult. One thing you can do is remove the engine and set it up to run outside the mower and check for the leak. I know there are dyes that can be added to the oil supply and using a special light to illuminate the dye, determine the leak location. I don't know if the oil has to be changed after the test or the cost of the dye and light but it is a alternative. Hope this helps.

 

Hydro stat oil is 20W50 motor oil.

Check the top of the pulley for the drive belt. If oil is pooling there it is likely the PTO seal. It could also be the sump gasket.

 

I agree with BFHFixit, most likely it's the bottom crankshaft seal. If so, there will be oil pooling on the top pulley over the PTO clutch.