That's what I heard as well Bob, 1956 is what was reported here but unconfirmed. Reportedly having mechanical problems, made it a couple hundred feet off shore and stopped. (No bilge blower on the boat, how can that be a good idea?) The little girl riding in the aft seat was blown out of the boat in the explosion, now in Grady Hospital Burn Unit. Very sad, and a good reminder that safety should be everyone's FIRST concern when renovating or restoring a classic! The authorities are investigating the accident to try and learn the cause.....
I don't believe the '50's boats had blowers, hence the vents on the gunwales to push air down and out the back. The Century's logo on the transom actually had a vent screen in the middle of it so the fumes and air can pass through it. Kind of like the old "Two Sixty air we ad in our old coupes.
A very common scenario. I have investigated a number of these and the circumstances are all very similar. It almost always happens after fueling but I've seen a couple where they hadn't fueled recently. But you have fuel either spilled or leaking into the bilge. The engine starts but there is no immediate explosion because the fuel air ratio in the engine compartment is too rich. As the boat starts moving, the natural movement of air through the engine compartment ventilation leans out the mixture until it reaches the upper explosive limit (The top of the range in which a fuel/air mixture will ignite - generally between 7:1 and 14:1 Air to fuel), and then it blows. A blower actually will actually cause it to happen sooner because it leans it out faster, unless you run it for 4 or 5 minutes before starting the engine.
Best prevention, your nose! Open the engine hatch and look and sniff. If you smell gas don't go.
Just to add about the blower. The rules for engine compartment ventilation were made in the Motorboat Act of 1940. But it only required natural ventilation. That was also when Backfire Flame Arresters were first required. The USCG did not require a blower until 1979, and then only on boats with a electric cranking motor (starter), but the industry standard for blowers had been around since the 1960's. The predecessor to ABYC, The Yacht Safety Bureau had required them, and I believe the National Fire Protection Assoc. NFPA did too. But they were rare until the 70's. Most small boats had only ducts and cowls for ventilation.
Thanks for the info/history on bilge blowers guys, good to know. After re-reading my post, I understand how/why it drew your responses. I often see inboard powered boats with their engine hatch open prior to starting, sounds like that WOULD be the safest way to check for leaks and fumes, even if the boat was equipped with a blower. My thoughts on the blower were that it would be similar to that of the bilge pump, may not be required but an excellent safety addition? Certainly not a guarantee you won't have a problem, but anything that we can do to help prevent or enhance a dangerous situation is worth consideration.
A big +1 for using your nose! I pop the engine hatch EVERY time I start the engine. A big sniff will tell you if there's gas or coolant leaking. I also check the oil level, coolant level, tranny oil level before every outing. Its always okay, but I need to KNOW.
The Century in my avatar is a '63 and had a bilge blower option. I went rounds with Century owners because my "bilge" blower is mounted under the bow deck and is piped via a 3" tube to the bottom of the motor. Century swore they are in the aft deck area but there is no room in that area because of the fuel tank. The boat itself was a replacement for one that suffered a similar burn to the water line in upstate NY in 1963.