I have been fixing up my motormarina sebring and it runs great except for one problem. The engine stops running after 10 minutes of riding. It runs great while at full throttle, but when I come to a stop at a stop sign, the engine stops and wont start back up. My carb is clean. The spark plug sparks. There is good compression. The gas is getting to the engine. Can anyone please tell me why the engine quits?