Outboard engines are known for being compact, light, modern, and reliable. It should be a good engine to convert. Aren't they a bit expensive? Engine prices and parts prices, here in the USA, are so high, you'd do just as well buying a Rotax or other aviation engine that didn't need converting. A motorcycle engine might be a less expensive starting point. Are 2 stroke motorcycle engines still legal for street M/Cs in your country?