Does anyone know of an "inline" product that would act like a check valve,
would work in a horizontal position, and fit my 5/8" id vent hose. I have
saddle tanks and the vent is only 4 inches or so above the top of the tank.
When I fill them full (two, 18 gal tanks) I wind up with spilled fuel out
the vents, all down the side of the boat (and in the water).

I was thinking of a pcv valve reversed, but even that seems to want to work
only in a vertical position.
Thanks in advance.
LD