fuel squirting out of nipple on intake manifold

[1999john25hp]

I posted an earlier question about excess fuel going into the carb, but I've tracked down the deeper problem. Fuel (maybe mixed with some water) is squirting out of the intake manifold nipple. That travels up a hose that goes to the primer syringe and tees off to a nipple on the top of the carb. It dies down after a few seconds, but I presume there's still something coming out of that nipple that shouldn't be.

Could this be caused by bad reed/leaf valves? Or something else?