While it would be possible to repair, a quick search found you can still buy the bushings, you would need to find a shop with the reamer, and even more difficult someone who has done it before. That's If the crank cleaned up ok. it would need to be cleaned and polished and measured. if it is under spec you may as well not go any further. not to mention if it has done crank bearings I would be suspect on the rings, bore, conrod etc. as it has obliviously had a lack of lubrication and/or been over revving.
To be brutally honest throw it away. Depending on the hoe, just find another motor. I recently did one for a mate that had the same problems, big play in the crank bearings. He had a Chonda off a pump that bolted straight on and was much easier to start, more powerful and reliable.
These little 3hp's are very common, you may even be able to find a donor engine, they are commonly pulled off reel mowers and sold cheap
