The extinguisher AND mount have to be USCG approved. Most home extinguishers would do just as well, but the point is that the approval means the extinguisher has a particular range and pattern of spray. I asked Kidde about this when I saw their new "kitchen" extinguishers at the store with no approvals on them. Why no approvals? Because the kitchen extinguisher uses bicarbonate instead of the regular powder, which corrodes hot stoves, and the spray pattern has been altered to blanket frying pan and stove fires, flatter than what the UL approvals require. For the given use, the product is better, but that makes it uncertifiable.
Similarly, the USCG certification
means it does fully comply, and that the bracket is strong enough to hold the extinguisher in a seaway, but easy to release when needed.
The phrase "bull----" comes to mind, there are so many bigger issues to be concerned with. But if you want to pass an inspection
, you need extinguishers that say USCG APPROVED somewhere on them, end of debate.
If an old extinguisher still shows good pressure, still weighs the correct weight, and still shakes (so you can tell the powder hasn't caked up) I wouldn't trhow it out, I'd just move it to another location and keep it as an extra extinguisher. The "liter" sized ones run out very quickly, it is not possible to have too many of them within reach.
And as already mentioned, if you've never used one before, take it ashore and USE IT. Put a fire in a pie tin, or ask your local FD to help you demo it. They make a blinding mess of yellow dust that you don't want to inhale, and if you know how they work you'll be prepared if you have to use one.
Don't bother refilling one if it is refillable, a new one costs the same thing as a refill and once they have been used, they tend to leak (slowly) after refills.
Too many on the boat? OK, throw one in the trunk of the car. There's always a home for the old ones.