I have a 1972 65 hp Merc outboard that stalls when you put it in gear and apply throttle. I have flushed both fuel tanks, replaced fuel, replaced fuel pump dismantled and cleaned both carbs, reset float, changed the spark plugs. It starts great, idles well and runs and revs great on the muffs, but when i put it in the lake and put it in gear, it stalls out...if i manually work the throttle, it revs right up, soon as i put it under load, it sputters and stalls... Please, I am at my wits end and don't know what to try next...can anybody out there help me???