Minnewaska, the inner face of the mushroom fitting should be sealed against the hull, this is what prevents water ingress.
Using these instructions as an example, they show where the waterproof marine sealant should go :
http://www.airmartechnology.com/uploads/InstallGuide/17-355-01.pdf
Think the OP mentioned he's going to do this.
Using these instructions as an example, they show where the waterproof marine sealant should go :
http://www.airmartechnology.com/uploads/InstallGuide/17-355-01.pdf
Think the OP mentioned he's going to do this.
