stats on vintage gas inboard boats igniting

I don't think this data exists. Also, if a gas boat explodes from a fuel issue, well, there usually isn't enough remains to pinpoint exactly where it came from.

Whether the tank or a leaky hose caused the leak doesn’t matter.

if every gas boat had a working gas fumes detector, and of people use a little common sense it wouldn’t happen

a leak alone will not cause the boat to go kaboom. It takes a spark which shouldn’t happen if the boat was maintained using marine parts. And common sense.

What Pascal said!

Bilge pump is another likely culprit. Someone has to hear the gas fumes detector's alarm in order to do anything about the leak. If it's a boat sitting in a slip, well.......

All marine electrical devices are ignition proof. A marine charger or a bilge pump should not cause an electrical explosion. It s the second safety layer.

Fumes detectors are pretty loud and anybody close to the boat would hear the alarm and should alert marina office

Should and is, are two entirely different things. I cannot tell you how many suspect electrical connections I've seen on gas inboard boats over the years. Owners think nothing of using electrical tape, automotive butt connectors and everything in between on bilge pump connections, battery chargers, and Lord knows what else.

I know... that was my point. Another flaw of the current boating certification... almost zero mention of the risk

and I can’t understand why the auxiliary passes boats for VSC without a fumes detector

Drip , drip , drip ... is at least a year of warning to the owner and or the boat yard that there is a big problem .
It should never get that far ... To a 12 V bells pump or whatever to set off the fumes.
Shame on the boat yard ... they should pick up on the problem right away.
In order to prevent an explosion.

I am always amazed at the lack of due diligence and care about boat yards And marinas. in general , many of them just don’t give a crap about the condition of a boat in their yard.
This is preventable before the drip , drip from the fuel tank... people turn and look the other way at times .

Can't believe it took all day for someone to come up with this. It's the cause in almost all gas boats going BOOM, especially in the spring when people have spent the winter just gassing their cars and going and they now want to get on the bay. Use your blowers when fueling, after and quite frankly whenever you're running. As for what would ignite? Batteries, starters, frayed ignition wires, someone turning on a light, etc. There's no shortage of sources. Get rid of the fumes.
Btw, spring is also a good time to get into the habit of watching whoever fuels your boat. I seen them stick the nozzle into rod holders, water tanks and holding tanks. And make sure their putting gas in a gas boat and diesel into a diesel.