Auto Discharge Fire Extinguisher

[tdonoughue]

Found this from BoatUS:

(after a section recommending dry chemical extinguishers over CO2 and other gaseous extinguishers for cabin fires...)

The same dry chemicals that are so effective in a boat’s cabin aren’t much use when a fire breaks out in the engine compartment. The reason has to do with how the two types of fires are fought.

Accounts of engine fires typically began with a warning?a burning smell, a loss of engine power, or even smoke trailing after the boat. If someone then opened the engine hatch to check out the trouble, he or she was usually overwhelmed immediately by flames and smoke. Fires need two things: fuel and oxygen. Opening an engine compartment hatch to look for a fire is like throwing gasoline on hot coals; it fans the fire with a rush of fresh oxygen.

The solution is to leave the hatch closed and fight the fire either with a fixed extinguisher in the engine compartment or with a portable extinguisher discharged through a fire port (a small opening into the engine compartment), which is why dry chemical extinguishers of any class are inappropriate. Blindly spraying a chemical extinguisher through a fire port does little or nothing to stop an engine fire because the chemical isn’t being directed toward the base of the flames. A gaseous extinguisher, on the other hand, extinguishes the fire by affecting the oxygen supply. The same extinguisher that wasn’t effective in the wide-open spaces of a boat’s cabin will be much more effective in a cramped engine compartment.

For this reason, among others, the ABYC recommends that either a portable gaseous extinguisher be provided near (outside) the engine compartment or a fixed gaseous extinguisher be used inside the engine compartment. In the event of a fire, either option eliminates the need to open the hatch.

Edited to provide full link: https://www.boatus.com/seaworthy/swybf.asp

 

[BoaterGuy]

That is very interesting. Im curious it looks like most of the marine extinguishers are Dry Chemical, at least all of the white ones. Is there anyway to get around spending $250+ on gaseous extinguisher?

 

[MNdrifter]

My local fire extinguisher company sold me a 5lb CO2 extinguisher for $160. Another $20 for a mounting bracket with a strap (default was just a hook) I'm planning to mount it to the floor under the starboard bow seat.
The 5lb CO2 is quite a bit bigger than a 5lb dry chemical.

 

[itsdgm]

I think the fire port would work well on the 21' Yamaha's around the same year as mine. The extinguisher wouldn't have to be at much of an angle (if any). It looks like the port could be installed right here on the engine cover hatch.

 

[MNdrifter]

The higher the better unless you go with CO2. I don't know why Yamaha would put them as low as they do.

 

[Noko]

How about modifying the extinguisher hose with a quick release adapter like on an air compressor hose coupling. Then add a longer hose to the adapter and you can keep the extinguisher upright. Or you could mount your extinguisher on the inside of the boat and run a hose to the fire port or engine compartment however you want. All you would have to do is pull the pin and fire the bottle. You could maybe add some piccolo tubing inside the engine compartment and have a better distribution system than just the fire port.

 

[BoaterGuy]

There actually is a fire port in the new boats in the center of the engine hatch... But as previously mentioned its hard to see where to aim a dry chemical extinguisher. I'm certainly sold on needing a CO2 one.

One observation however is that older boats that are carbureted were more susceptible to fires due to the open style of the intake that allowed fumes to escape. With fuel injection I feel like this risk is significantly lower. Therefore, by design these boats have a lower risk of engine fire than any of the carbureted boats out there. I don't ever smell gas when I'm on this boat, whereas I did all the time with my Merc 3.0 non EFI.