It is possible to make part 103 with electric start on this engine. The 3202 makes an excellent replacement for the 503. The quicksilver Sprint and Sport models are unique in the industry in that they use a reduction drive built into the airframe. The larger and more popular (now days anyway) Subaru engine is the 2.2 Liter, which weights a whopping 315 lbs !!!!! One of these engines, professionally overhauled, can be a very inexpensive and reliable engine for use in a Quicksilver. This engine can be purchased brand new for under $3000 with all the necessary accessories, and can be purchased used or overhauled for considerably less. It is noted for its extremely light base weight of 35 lb (16 kg). In our application, some of the factors that are very important to us, are the weight of the engine, and not only the power, but the thrust it is capable of producing. There are several engine options that will work nicely here. System for Multiplexing Acoustic Emission (AE. It has been done and an installation package is available. The cylinder walls are electrochemically coated with Nikasil. Who can afford a $25,000 Lycoming to put on a $15,000 airframe to fly 50 hours per year? Engines: Rotax TOC 20-hp 4-cyc w/RPM of 2000 at blades, recommended 3/50" (Adam Gibson) Rotax 277: 26 HP It will soon become difficult to get certain parts for the 447. FYI: Here is an engine weight comparison. The Rotax 503, 52 HP engine was probably the most popular engine in the two seat ultralight type aircraft for over 25 years. If you can live with 50 HP, it is a much better engine for this application. A fuel caddy can be purchased on Ebay for under $200. Warranty: The warranty on a Rotax 582 is 18 months from the date of purchase. After a couple years of that, I installed a 3203. Another option for this airframe as well may be the Hirth F23 once we are able to get an installation setup for the Challenger airframe. The Hirth F-33 is a single cylinder, two stroke, carburetted aircraft engine designed for use on ultralight aircraft, including powered paragliders and ultralight trikes. In other words, we use a belt drive or a gearbox to act as a transmission to spin the prop slower, but with much more torque. It is possible to order it from the factory with a Briggs and Stratton four stroke engine. This option accomplishes two things. While this engine will be an excellent candidate for this airframe, the installation still has some bugs to work out. It’s only disadvantage compared to a 447, is that it is significantly heavier, around 10 lbs. You can expect to spend $15,000 or more to reposer with a new 912. We would be looking at about $3000 and we have an engine that is like new and ready for another 1000 hours. They have the bugs worked out, and if the manual is followed closely and it is operated properly it should be pretty reliable. (it might also break out of the top speed of part 103 without a throttle stop though). At 50 hours per year, 20 years down the road we would have 1000 hours. Choosing fuel injection is a personal preference and may depend on the area you fly as well. Since it is an air cooled engine it does not suffer from the downfalls of liquid cooling. (the speed at which the crankshaft is turning, measured in Revolutions Per Minute.) People who do not understand two stroke engines and tuning, really do not need to with fuel injection. A complete airframe including a propeller can be had for just over $10K. The warranty does not consider the hours of operation, only date of purchase. As far as part 103, if you wanted to be technical, if the battery has quick disconnects it does not have to be considered part of the airframe for weight purposes since is it not permanently mounted. However, my recommendation would still be to stay with a 3203. It will install easily in nearly any application that the 503 was used in, and will out perform it with no weight gain. It performs very well, with a high roll rate, and higher wind capability. It also started out as a sled engine that was converted for aviation, but in the early 90’s Rotax came out with a dedicated aviation version that featured dual Ducati ignition, Bing carbs, a stronger crankshaft, and the new provision 8 which allowed the use of the B, C, and E gearboxes. If we simply put a prop on a two stroke, it will not make very much thrust because it does not have very much torque, therefore cannot swing a very big propeller.