My 79 evinrude 70hp runs fast at idle, but has no power in gear. when in gear it putters but dosen't open up?

You can get carb kits from auto parts store i bought mine from oreillys it was 19 dollars and i have a 115 hp evinrude.Pretty easy to rebuild and clean your screen on your fuel filter and check primer ball make sure its not collapsing because they can when get old.