Having trouble with my 89 merc. 25 hp outboard. Problems started with a failed fuel filter that allowed sediment into carb. Tore carb down and cleaned, new fuel tank and fuel/water separator and new plugs. Motor ran good at first startup after carb rebuild but then developed the problem of falling flat on it's face at anything past half throttle. Now getting fuel out of the exhaust at first start and am wondering if I have a needle valve problem. All help and advice is appreciated and thanks in advance.