I have a late 70s model evinrude 75 2 stroke it will start and idle fine but when I put it in gear it almost dies or does stall... If it doesn't stall it will coast slowly and eventually after coasting and bogging down it will begin to pick up and finally take off and get up to speed... The guy I bought it from said it had new carbs and they look fairly new any suggestions as to what it could be?