Parsun is good. Been around for a while, they are indeed based on Yamahas.
2 Stroke, been told that some Yamaha guys buy the Parsun part to use for their Yamaha as the parts are cheaper.
Force, dont know much about them, but also heard that Mercury had them at some stage, but dont know how true that is?
Here is what I got of the interweb.....:welcomesea:
The Force name appeared when U.S. Marine, makers of Bayliner boats, purchased the Chrysler outboard plant in 1984. Chrysler continued to make engines under the Chrysler marque, however. U.S. Marine owned the Force brand until 1988, when Mercury Marine acquired it. Mercury Marine dropped Force Outboard in 1996.
http://continuouswave.com/ubb/Forum1/HTML/010046.html