I had exactly the same thing clog my fuel system after 10 years of running the OEM fuel line from the tank to the engine on E 10 Ethanol. Time for a new line and squeeze bulb (OEM seems to work best), and complete cleanout (best to just replace them) of internal (to the engine) fuel lines and components like fuel pump (kit) and fuel filter......assuming you have one adjacent to the engine intake manifold.....if not, go on through with new carb kits. Be sure you soak and blow out with compressed air and wire where you can to open any clogged orifices.
On the suggestion to use your boat more, there may be something to that. I didn't run mine but a couple of hours every few months (at WOT as long as I could find open water) but kept Sea Foam in it for engine hygiene which did a nice job to keep carbon at bay and keep the Looper wedge rings loose.
