I have been working on an old evinrude 25hp. I've gotten it running but it spits, coughs, and sputters and every time I throttle it back to a low idle speed it dies. I've sprayed the carb down with cleaner and added sea foam to the tank. All that helped to get it running.. would stay running at all before that. Anyone have any suggestions on what else I can do to get it running smoothly?