I have the Alpha .45 and the newer .46 and like 'em both. Strong runners, and I took the limiter collars off first thing...A friend has the new .61 but hasn't run it yet. If it runs a well as the others, it will be a real nice engine. My .455 alpha engine (in a Cermark Bobcat)today turned an APC 10x7 @ 13,100 on 10% w/ an aquacraft (Tower) muffler...