Same here, my boat does not leave without a quick running visual check. Heck i would think you'd be crazy if you didnt do that. Only takes i few minutes

Absolutley agree that with the correct fuel / air mixture, a powerful explosion is indeed possible. Also agree that the smell test - particularly in the lowest point in the bilge where fuel vapors collect - is a great tool.

If you have a bilge full of fuel though, the air / fuel mixture is way to rich to ignite. Sometimes opening the hatch can add enough air to get you into the correct range to blow. Properly installed bilge blowers suck from the lowest point in the bilge and replace it with fresh air. One theory states that you're actually more efficient in moving air with the hatches closed. Of course with enough fuel in the bilge, all bets are off. That may have been the case here, but we're arm chair quarterbacking.

Here's my point on that being a fuel fed fire though. Notice the massive flames and black smoke? Black smoke means a fuel rich mixture. There's lots of fuel feeding that one. (And yes, fiberglass & resin are decent fuels.)

I agree were just speculating as to what exactly happened but the size of the fire seems to indicate that possibly one of the motors or electric fuel pump was running which would feed fuel to the fire after the explosion. That and with the hatches probably gone oxygen (air) would also increase the intensity of the fire.

Below the explosive or flammable range the mixture is too lean to burn and above the upper explosive or flammable limit the mixture is too rich to burn. The limits are commonly called the "Lower Explosive or Flammable Limit" (LEL/LFL) and the "Upper Explosive or Flammable Limit" (UEL/UFL)

For gasoline the explosive limits are fairly low with the range being 1.4% (LEL/LFL) to 7.4% (UEL/UFL).

Bilge blowers are much more effective when the hatches are closed but checking for obvious leaks before firing up only takes a second and can save not only your boat but possibly your life.

On a somewhat unrelated incident where it was a natural gas explosion in a home the question was asked to one of the fire investigators what the possible ignition source was. His reply was just about anything that creates an arc or spark from a faulty light switch to the pilot light on the water heater...

Military Fuel/Air explosives are sometimes called the poormans Nuke.

Like the MOAB (Mother of all Bombs)....

the propane bom...heard about that...

That is absolutely awful but at least they were not hurt. Does this happen with outboard boats as well? For some reason I always thought for an explosion you need to have some kind of igniter, spark? Are you guys saying air/gas fumes can lead to a fire just by themselves? Or does that usually happen right when you start the engine and you have gas fumes in the engine compartment? I'm really not too familiar that's why I'm asking.

On an outboard the batteries are in the bilge as is the fuel tank, get a loose connection to the battery and the same thing can happen.

What a bad break. I hope his insurance doesnt give him a hard time, losing that boat is bad enough.

Very true!