hi i have a 1979 70 horse johnson. it has ran fine up to today. start it up runs ok try to go and it just loads up i think. wide open the motor is blowing lots of exhaust out and i just barely move. the prop is fine. i replaced all the fuel lines the fuel the spark plugs and the vacuam line coming from the motor to the fuel pump. it is just the same no difference. what might be the chance it is the fuel pump.