It will need an engine replacement. Take the engine's model, type, and code number to a Tecumseh dealer and look up the price of a replacement engine and a short block. If you can remove the parts that bolt to the block and put them back on you can get by with a short block. The short block will need the head, sheet metal, flywheel, gas tank, muffler, carburetor and intake manifold, linkage, and ignition all switched over to the new short block. We used to sell a lot of those at the shop where I worked. Just to make you feel better, once, someone bought a discounted lawn mower from a department store chain. The mower had been returned as defective, and it wouldn't turn over. I took that oil plug out and oil shot out for quite a while. I removed the spark plug and it was soaked in oil, and I was able to turn over the engine at this point. A cylinder full of oil shot out the spark plug hole. I cleaned up the mess, and spun the engine over a few times to clear more oil from the ports. I put the right amount of oil in it and started it up, outside. Everything disappeared with the smoke, but it did clear up. He had a new lawn mower for a cheap price, even paying us to empty it of the excess oil.
