Chad, that engine is an Echo 61cc CS-610 chainsaw that was made in the early 80's for about 4 years. I have had and converted many of them and they are all strong as you would expect from Echo saws. They were on the heavy side for a saw but the torque was incredible. I just sold a running saw I had used for a few years now so I can say that they were powerful in that application. They are very hard if not impossible to find anymore. I have my prototype still ready to run and a couple of bare crankcases left that I never converted. I ran my prototype with a 22/8 prop but it would easily turn a larger prop. Here are pictures before and after the conversion process.

Tim