I have fitted a brass barbed fitting to my outboard's leg. It is higher
up though, where the exhaust relief port is located. My outboard is in
a semi closed well and this port would fill the well with smoke and
starve the motor of air.
The barb has a hose fitted which leads the fumes out the transom via
another ( plastic) barb.
There are no corrosion problems after about 6 years use, mainly because
the barb gets well oiled from the two stroke exhaust.
Klaus