Through deck filler

From BSS guide
So, no, IMO 

Its a funny looking thing, looks a bit like a radiator cap. Not immediately obvious how it is meant to be attached. I suppose the vent would be plumbed out of a skin fitting as it appears that after installation the overflow/vent outlet would be below the deck.





Eta maybe the vent elbow can be rotated to point upwards? If its threaded this would cause problems. It must be removable or it can't be mounted in a 50mm hole ??

Or does one just bodge it in with a bit of stikaflex

It'd need to have a flame arrestor on it anyway. One of my boats subject to BSS has a vertically mounted vent with a round brass fitting on top with two horizontal holes with gauzes in them. Other boat has one of these but mounted horizontally.

some boats have the vent in the top of a hollow mooring dolly.