I did a search for posts and general web sources for PWC engines in airplanes. There is nothing here that I could find and precious little on the web. That probably means it doesn't work, but let's take a look at this option. As I continue to research the engine options for a small plane build, I keep circling around the usual suspects and am routinely shut down by the usual ridiculous prices. I can buy a 350hp LS1 Corvette crate motor for less than a 50hp Hirth. It's ridiculous how much the word 'aviation' costs. This frustration leads me to the larger world of engines outside those marketed for aviation. And while I'm not stoked about 2-strokes, I dislike the power/weight ratio of half VWs and the like. But, I trust the name Yamaha, having owned and ridden many of their motorcycles and PWCs over the years. As one of the most prolific engine manufactures on Earth, their merit is proven. Enter the Yamaha 701 2cyl/2stroke Stock horsepower is 63 to 73 depending on year of manufacture with popular mods the hp is up to 80-85 Max HP achieved at around 6200RPM Weight is 36kg/80lbs Even the older but very similar 650 gets 50hp stock. The newer 790 gets 90hp stock. These of course, are liquid cooled/open loop systems, so we would need to convert to a closed loop and add the weight of a radiator and coolant. The advantage may be far better cooling than high output, air cooled 2-strokes are known for. I'd be happy with a little better. We would also need a PRSU which adds some weight - common in 2-strokes. To my mind, we have an engine with some of the same considerations as a Rotax 582, but we can get it rebuilt for $595 (plus core)..., a tenth what a rebuilt 582 costs. I'm certain I am wrong and that plenty of dialog exists to prove it, so please educate me so I can move past this 'too good to be true' flight of fancy. Thanks!