The BoatUS Foundation for Boating Safety and Clean Water helps debunk some myths about fire extinguishers and their use.

https://www.offshoreonly.com/article...eling-the-fire

There are also several automatic permanent installation type systems that are meant to address the fire before even opening the hatch. Halon is similar to Kleenex or Zerox (as far as name recognition), but since the early 1990's Halon has been outlawed for use in a new system. There are various agents on the market, most of which work similar to Halon but are labeled as "clean agents" that do not leave behind a caustic residue.

FM-200 is probably the most common.
Novec 1230 is another among others.

The smaller ones will operate much like a sprinkler head where as a small fusible link will melt at a pre-determined temperature and expell the agent. There are also auto/manual combinations along with larger systems that have a releasing panel or controller to determine when the agent should be released.

Any new system is sized based on the volume of the protected space (the bilge, L X W X H) and are relatively inexpensive considering the alternative.

Actually Myth 3 is not totally correct. Hand Portable Fire Extinguishers require at a minimum an internal cylinder exam every six (6) years and need to be hydrotested every twelve (12) years if it's a clean agent or dry chemical extinguisher. For CO2 extinguishers they require to be hydrotested every five (5) years. Most state require that the extinguishers are inspected and tagged every year to insure that they are proper operating condition. These are requirements set forth by the National Fire Protection Association (NFPA) and US Coast Guard which regulates Marine applications.

Fixed Systems like in the Bilge typically are Clean Agents (Halon, FM200 (HFC-227ea and Novec 1230) should be inspected annually to insure the pressure is correct and the weight of the agent hasn't changed. A 10% loss of agent weight requires that the system is taken out of service and repaired and refilled.

As mentioned above the automatic fixed systems are pre-engineered to cover a specific volume and when looking at some of the boats that I've owned they are typically undersized. There are also a couple issues with how these systems are installed and designed. Most do not having the ability to manually actuate the system, which in some cases would greatly assist in actuating the system at the first indication of a fire. The other item which is probably the hardest to overcome is the un-closable openings that are present in the bilge for air induction for the engines. Clean Agent fixed systems require that the volume is totally sealed to allow for a certain concentration to be achieved to suppress the fire. With the air intakes coupled with a boat moving at high speed the air in the bilge will exchange very rapidly. If the system were to operate due to the head fusing (high heat) while at speed all of the agent could be sucked right through the bilge and not have the ability to suppress the fire. These types of clean agents are designed to fully empty in ten (10) seconds or less. Only CO2 type systems allow for a longer discharge duration but these are rarely used in pleasure boats do to the size and weight of the cylinders.

Almost sounds like you know that from experience

Unfortunately yes. Plus, I work in the industry also.