How to Check, Mount and Replace Boat Fire Extinguishers

Pull every extinguisher off the boat: the ones in brackets, the one in the cabin, and the forgotten one under the V-berth. You will check each one against the same list. If you find more than you need, keep the best ones in service. The USCG says expired or older units can stay aboard as extras, as long as you also carry the required number of good ones.

Look for the words "Marine Type – USCG Approved" on the label. Underwriters Laboratories (UL) approves marine extinguishers for the Coast Guard, so you will also see the UL mark. A household extinguisher without the marine approval does not count toward the requirement, even if it is the same size.

• Model year 2018 and newer: you may only count extinguishers rated 5-B or 20-B (they may also show A and C ratings) that have a date of manufacture stamped on them. Older labels that say only "B-I" or "B-II" do not count on these boats.
• Model years 1953 to 2017: you may carry 5-B or 20-B units, or older B-I or B-II units, as long as they are in good and serviceable condition.
• A 10-B counts as one 5-B, not two. Only a 20-B replaces two 5-B units.

Disposable (non-rechargeable) extinguishers must be removed from service 12 years after the date of manufacture. The date is usually stamped on the bottom of the bottle or printed near the UL label, sometimes as just two digits for the year. Many labels say outright that the unit must be removed from service within 12 years. A 13-year-old disposable bottle is expired even if the gauge still reads green.

Rechargeable extinguishers (usually metal valve heads, a service tag and a label saying rechargeable) do not expire at 12 years, but they need annual maintenance by a certified technician. The first service is due one year after the date of manufacture, and the tag should show it.

Hold the extinguisher upright and look at the gauge. The needle must sit in the green "operable" range. If it is in the red (either side: undercharged or overcharged), a disposable unit must be discarded and replaced, and a rechargeable unit must be serviced and re-tagged. Some small units use a push-button pressure indicator instead of a needle; follow the label for how to read it.

Run through the other Coast Guard "serviceable" checks:

• Locking pin firmly in place, with the plastic tamper seal unbroken. A missing seal can mean someone squeezed the handle.
• Nozzle or hose clean and clear: no mud dauber nests, spider webs, salt crust or cracked hose. Powder in the nozzle means it has been used.
• Body without heavy rust, deep dents, or a swollen or cracked bottom. Light surface rust can be cleaned; corrosion that pits the metal means replace it.
• Label still readable, including the instructions.

Most small marine extinguishers are dry chemical. Engine vibration and pounding over waves can pack the powder into a solid cake at the bottom, which may not come out when you need it. Many fire equipment technicians suggest turning dry chemical units upside down once a month and feeling or listening for the powder to shift. Check your extinguisher's label and manual: some makers recommend a gentle shake or tap with your hand, and none recommend hitting the bottle with a hammer. If the powder never seems to move, have it inspected or replace it.

The USCG strongly recommends mounting extinguishers in brackets, although it is not required; what is required is that they are readily accessible. If the label says the unit is approved only with its bracket, use that bracket. Good locations:

• Near the helm, where the driver can grab it without leaving the controls
• Near the cabin or galley exit, so you can fight a fire on your way out, not trapped behind it
• Outside the engine compartment, never inside it (you cannot reach it if that is where the fire is)

Use stainless screws or through-bolts into solid material, not just a thin liner. Mount the bottle so the gauge faces out and the quick-release strap opens with one hand. Keep extinguishers out of direct sun if you can, and away from where people sit and kick them.

Some extinguishers (mostly water or foam types) must be protected from freezing; the label will say so. If you store the boat in a cold climate, take those home for the winter. Dry chemical units are generally fine in cold storage, but check the temperature range on the label.

• Disposable unit used, in the red, expired, damaged or missing its seal: replace it. Ask your local fire department or household hazardous waste program how to dispose of the old one; many take them, and some ask you to discharge it fully first in a safe place.
• Rechargeable unit used or out of range: take it to a certified fire extinguisher service company to be recharged and tagged. Also take it in once a year for its annual maintenance, even if it was never used.
• Older B-I or B-II unit on a 2018 or newer boat: replace it with a date-stamped 5-B or 20-B.

Larger boats often have an automatic clean-agent system in the engine room. These are designed to discharge on their own when the space reaches about 175°F and to empty in under 10 seconds. What you can check yourself:

• The helm status light or panel shows "charged" or green, and nothing shows "discharged" or a fault
• The bottle is secure in its bracket and has no obvious damage or corrosion
• The engine shutdown system (if fitted) has not been bypassed with the override switch left on

Clean-agent gas does not stop a running engine. If the engines and generator keep running, they can suck the agent out of the space and the fire can come back. That is why many systems include automatic engine shutdown. Weighing or servicing the bottle is a job for an authorized service technician; follow the schedule in the system's manual.

Show everyone aboard where the extinguishers are and how to use them: Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep side to side. Write the check date on a tag or label on each unit and log it in BoatMend so you get a monthly reminder.