My Boat has sat in storage for approx. 4 years. Fuel was immediately emptied and new added. When on the water right after purchase, the engine would start fine, idle rough, and occasionally bog down near WOT. I changed props, installed new plugs and fuel filter. Problem seemed to be fixed, boat ran fine for couple of months. At WOT, 5500 rpm 52mph. Now problem has reoccured, but more severe. Cranks fine, idles very rough (motor kicks and knocks), bogs immediately, rarely gets on plane, catches up every so often and surges forward. I have very recently done the following: removed all 3 carbs and cleaned thoroughly, reinstalled with new gaskets, replaced most all of the fuel hoses/lines, new plugs. Same problem, maybe worse. Could be carb link & synch, but there has to be more to it. Any suggestions?