Great site and I have been lurking and reading for a while. I have a 1993 Bolens hydro ST125 with a Kohler Command 12.5 engine that finally wore out on me. The tractor itself is in good shape; no rust on the deck, newer tires, etc. I will be retiring and moving to a condo in about four years and I was considering a fresh motor to get me through the next few years rather than buying a new tractor. I guess I'm also a little sentimentally attached to it as it been basically trouble free for 16 years. Seems a waste to just junk it because the engine is bad. I was wondering if I could just drop in a replacement engine, either a Kohler Courage or B&S without a lot of hassle. I know the shaft needs to be the same, in this case 1" x 3 5/32", and I could drill new mounting holes if I needed to. But is there anything else I need to look for or is a swap on a small tractor fairly easy? Any other engine suggestions? Thanks.