i have merc 1967 500 50 hp starts and idles fine but when i put it in gear it dies so i idled it up but the slowest i can troll is 4mph and ihave to choke it to take off . new line and tank. if you think its the carbs. please give me a diagram because it looks hard to get to them a lot of stuff in the way. S/N 2626085 THANKS