Long time ago I was replacing a burner valve on my yacht stove, doing the soap bubble test afterwards I still had a tiny leak. Being immeasurably young and stupid I decided to "see what would happen" if I lit this little bubble up, the "scientific method".
Okay, this is a very very minor slow leak, taking minutes to make a one inch bubble, I mean how much pressure could a soap membrane an inch in diameter contain, so hardly any propane, right?
Hey, I was smart enough to open the port above it and slide the main companionway hatch back, nice quiet still morning....
The "fireball" was about a foot in diameter
Never search for a gas leak with a match.
There are plenty of stories about boats in marinas where you'd see your typical Tupperware 30 with the whole deck sitting on the hull slightly askew as if it were somebody's partially completed kit, its always a case of the hull filling with a little bit of leaked propane and someone lights the stove. In most cases nobody is seriously hurt but the poof that happens is a bit of a shockwave an hopefully it is over and done with before anything catches on fire.
...Chrissi