Take model and serial number to a small engine shop and they can order a short block for you. You will then have to transfer the head, carb,muffler,flywheel and coil to the short block. It comes with all the gaskets needed and it is much cheaper than buying a crated engine. If you are not comfortable transfering the parts to a short block then buying a crated(complete) engine is the way to go. Any small engine shop that is a Tecumseh dealer will be able to order both in for you.