One Fire Extinguisher will NOT keep the USCG happy! All boats over 26' need at least 2 B-1 (or 1 B-2) extinguisher, more is always better (within reason?).After a while the powder cakes up in the bottom of the bottle. Pressure reads ok but nothing will come out when you pull the trigger.
By the way, one FE might keep the Coast Guard happy, but when you need one ten is not enough. I have six on my 36 footer, only required to carry two.