Fresh set of NGK's, Seafoam (b12 Chemtool is a cheaper option and honestly think it does a little better as a cleaner), and NO ETHANOL. That stuff will ruin your engine if it hasn't started to already. Your motor is probably old enough to not be built to handle it. I think new plugs and some cleaner with real gas instead of shine will make it a scalded ape again tho
Here's something you can do with the Seafoam to give your motor a shock treatment. Take a gallon gas can and pour the whole can in it. Fill the rest of the way with gas. Unhook the line from your fuel filter if available or just stick your bulb in to suck it in there. Fire it up and watch the smoke show. After running for about 15 mins or so on the hose pour the rest in your tank and hit the lake. Truth be told I think people use too much Seafoam during regular operation and should only be used a couple times a year. Just opinion so don't shoot.