With all of that oil on the interior, I would change the air filter. It is almost surely plugged by oil vapor and dust. Then, to address the
So my new issue is it shutting down with an over heat even with a light load. I have added coolant, tried to run it with both the doors closed and open.
I removed the thermostat hoping to solve the problem but that didn't change anything. On a whim I decided to drain and refill the radiator. When I opened the stop cock nothing came out so I removed the stop cock and found something interesting.
In the hole there was a thickened black substance. I would have called it oil but it was really thick and easily washed off my hands with a little soap. After cleaning it out the best I could with a stick, I ran the engine for a few turns and nothing came out of the hole so I figured it was gooped up pretty good. I pieced together some garden hose and commenced to flushing the radiator from the top. After a bit the water started to come out of the bottom and finally ran clear.
Just my luck, power returned to the island as I was finishing the flush job.
Not really sure what that goop was though.
With all of that oil on the interior, I would change the air filter. It is almost surely plugged by oil vapor and dust. That will give you both black smoke and failure to carry full load, even if it looks OK. As far as the radiator and cooling system are concerned, if the stuff looked oily the old trick is a few spoonfuls of Cascade (Non-foaming) dishwasher soap into the cooling system with water, run it for a few hours, and then drain and flush with plain water. I wouldn't run straight water in the unit for any length of time, I'd change it over to low silica HOAT as soon as it's cleaned out.