On Tuesday, 3 April 2018 12:59:42 UTC+1, Harry Bloomfield wrote:
More effective, would be something like a vacuum cleaner hose, which
you could drop to the bottom and suck the gas out - except for the fact
that the gas would then pass through the vacs motor. LPG leaks in boats
are a deadly combination, due to it being heavier than air.

I think my Karcher (and some other tub vacuums) have separate openings for motor intake and exhaust cooling fan, and vacuum suction exhaust air.

Not sure I'd risk it though.

Owain