Boat Fire Extinguishers: Types, Ratings and Where to Mount Them

Under 33 CFR 175.320, a recreational boat 65 feet or under must carry a minimum number of portable 5-B extinguishers set by length: one for boats under 26 feet, two from 26 to under 40, three from 40 to 65, with one fewer where a fixed system protects the machinery space. Some small outboard boats are exempt. The extinguisher must also be approved, easy to reach and in good condition. This is as read on the eCFR in October 2026, so check current USCG and state rules.

What the Coast Guard rule requires

The text of 33 CFR 175.320 sets minimums for recreational boats 65 feet or under in a table by length. The table counts portable extinguishers with a 5-B rating.

The rule notes that one 20-B extinguisher may be substituted for two 5-B extinguishers, and that extinguishers with larger numerical ratings or multiple letter designations can be used to meet the table. It also exempts boats under 26 feet propelled by an outboard motor if their construction cannot trap flammable gases or vapors. Larger vessels have a separate table.

This summary is not legal advice and the rule can change. Check the current text and your state's rules, and read the boat safety equipment guide for the wider picture.

Which parts of a boat trigger the need

The rule lists conditions in a boat's construction that call for extinguishers, and others that do not by themselves. They are useful for judging your own boat.

If you cannot tell whether your boat meets the exemption for small outboard boats, ask the manufacturer or the Coast Guard rather than guessing. Many owners carry extinguishers anyway.

What counts as usable

The Coast Guard rule in 33 CFR 175.310 says each required extinguisher must be on board and easy to reach, be an approved type, and not be expired or look as though it has been used. It must also be in good working order: any pressure gauge in the operable range, the lock pin firmly seated, the nozzle clear and no significant visible corrosion or damage.

The same section says that if the nameplate says an extinguisher must be protected from freezing, it should not be kept where freezing is likely. Extinguishers with toxic vaporizing liquids do not count as required equipment. Read your extinguisher's label for its approval markings and the maker's service and replacement notes.

Types, sizes and mounting

The rule counts by rating, so the label is your guide: look for the 5-B (or higher) rating, the approval markings and the maker's notes. Bigger units give a larger rating, but they weigh more and take more space. A common approach is one near the helm and another near the cabin, and your boat's layout decides.

Mount the extinguisher in the bracket the maker supplies or specifies, with corrosion-resistant fasteners, so it does not move in rough water. Put it where you can reach it quickly without passing through the area where a fire would likely start, such as the engine space, galley or fuel area. That is a practical judgment, not a rule, so also read the maker's instructions and talk with your marine surveyor if you have one.

If you are buying new, consider a bracket and a unit sized to the space. A bigger unit may meet the count with fewer purchases, but a smaller one can be easier to reach and handle. Also check the label for any storage temperature note, because the rule says an extinguisher marked for protection from freezing should not be kept where freezing is likely.

Keep the extinguisher out of damp bilges and away from sources of damage. Tell everyone aboard where it is and how to use it. Our guide to organizing safety gear on a small boat shows how to keep it reachable.

Check and replace on a routine

Plan for the crew as well as the hardware. Everyone who may need to act should know where each extinguisher is and have read the instructions on its label. Do this before you leave the dock, in daylight, with the extinguisher in its bracket, rather than in the middle of an emergency.

If you ever use an extinguisher, even briefly, treat it as used. The rule says a required extinguisher must not look as though it has been used, so replace it or have it serviced as the maker directs. Do not put a partly used unit back in the bracket and hope for the best.

Check each extinguisher at the start of the season and after rough days: gauge in range, pin seated, nozzle clear, no corrosion or dents. Replace any that are expired, discharged, damaged or fail the checks, following the maker's label for service or disposal.

For a complete picture, see what safety equipment is required on a boat and the complete boating safety gear guide, and keep a first aid kit aboard too.