i have a 1984 evinrude 185 hp that ive been chasing a problem with, i got the boat and the head gasket was blown. replaced both head gaskets and now the boat runs good...sometimes. it has new fuel filter and fuel pump. i can not find any dry rotted lines or air leaks. the tank strainer is also clean. Now there is a smaller fuel filter on the side of the engine that the fuel flows through, this thing never stays full. it usually sucks down till its almost empty. is it supposed to stay full? the one on my smaller mercury out board always stays full. the boat will run good but is very hard to get to wot and is very picky on when it does. also surges alot if im giving to much throttle. any ideas? im thinking a air leak at the plastic fuel filter housing on the side of the engine . thanks