leaking carbs

[johnrthomas]

I bought a boat with a 40 hp 1996 merc outboard that had sat for a couple of years. It didn't run well so I rebuilt the carbs. I have rebuilt them several times and used new gaskets twice now. Every time I rebuild them they both leak. I will check them before I install them by turning them upside down and blowing into them. I also test them by hooking them up to a bulb and can of fuel. They don't leak until I put them on the boat. They start out leaking slow and then tend to leak more as I let the boat run. They seem to be leaking out of several places on the carb. The boat will run but and will rev up when not in gear but when under load the boat will bog down and die.
I replaced all the plugs and have checked the spark it is good. I thought maybe a reed valve was stuck open and causing fuel to be forced out the cabs but I checked compression and It's fine.
I have had two local mechanics rebuild the cabrs and they still leak. I took the boat to a merc dealer (which is a 2 hour drive) and he thought it was the fuel pump and ordered a new one which I put on and still the carbs leak.
They seem to leak out the vent jet and the bowl gasket. I bought the merc manual after I rebuilt them the first time and they leaked. Sometimes I think they leak out the bowl gasket where there is a brass baffle. What is the baffle for?
Any thoughts on why they would just leak on the boat?