I had the same issue with my 1980 50 HP Johnson. I was told I needed tuneup costing about $350.00. A friend of mine suggested trying Lucas fuel injector cleaner first. He didn't know the additive but it is the ONLY cleaner he found that actually works. I've been up and running just fine. Been out 6 times since the treatment. I also have an additive (StarTron fuel treatment) that neutralizes the ethanol in the gas. I brought mine from WI.,, don't know where to get it here. Good Luck!!