When I first unload boat it starts and idles fine, but for the first 15 minutes or so it runs really rough, rpms bouncing all over the place. Will barely get on plane. Then after that it runs perfect. It only seems to do that when its cold or has set for more than 4 or so hours. It has a freshly rebuilt motor with 13 hrs on it. Seems to be progressively getting worse. Its bot beeping. New plugs and wires. Please help. Thanks