I agree with the ethanol response. I forgot my Merc used to bog down but I switched to Chevron exclusively which has Techron vs. ethanol and I remember that I started getting better response from the engine. I'd swear by it. No ethanol anymore for my boat. If you have a clogged carb I have friends that recommend Quicksilver carb cleaner or Sea Foam. I have also changed the inline fuel filter but there is also an internal fuel filter inside the cowling. I believe it is along the fuel line after the fuel pump. Make sure you have zero leaks when replacing your filters.