There are different types of dry powder. Most commonly the yellow dust, but here's from the Wiki folks:
Monoammonium phosphate, also known as "tri-class", "multipurpose" or "ABC" dry chemical, used on class A, B, and C fires. It receives its class A rating from the agent's ability to melt and flow at 177 °C (350 °F) to smother the fire. More corrosive than other dry chemical agents. Pale yellow in color.
Sodium bicarbonate, "regular" or "ordinary" used on class B and C fires, was the first of the dry chemical agents developed. In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That is, the gas drives oxygen away from the fire, thus stopping the chemical reaction. This agent is not generally effective on class A fires because the agent is expended and the cloud of gas dissipates quickly, and if the fuel is still sufficiently hot, the fire starts up again. While liquid and gas fires don't usually store much heat in their fuel source, solid fires do. Sodium bicarbonate was very common in commercial kitchens before the advent of wet chemical agents, but now is falling out of favor, as it is much less effective than wet chemical agents for class K fires, less effective than Purple-K for class B fires, and is ineffective on class A fires. White or blue in color.
Potassium bicarbonate (aka Purple-K), used on class B and C fires. About two times as effective on class B fires as sodium bicarbonate, it is the preferred dry chemical agent of the oil and gas industry. The only dry chemical agent certified for use in ARFF by the NFPA. Violet in color.
Potassium bicarbonate & Urea Complex (aka Monnex/Powerex), used on Class B and C fires. More effective than all other powders due to its ability to decrepitate (where the powder breaks up into smaller particles) in the flame zone creating a larger surface area for free radical inhibition. Grey in color.
Potassium Chloride, or Super-K dry chemical was developed in an effort to create a high efficiency, protein-foam compatible dry chemical. Developed in the 60s, prior to Purple-K, it was never as popular as other agents since, being a salt, it was quite corrosive. For B and C fires, white in color.
Foam-Compatible, which is a sodium bicarbonate (BC) based dry chemical, was developed for use with protein foams for fighting class B fires. Most dry chemicals contain metal stearates to waterproof them, but these will tend to destroy the foam blanket created by protein (animal) based foams. Foam compatible type uses silicone as a waterproofing agent, which does not harm foam. Effectiveness is identical to regular dry chemical, and it is light green in color (some ANSUL brand formulations are blue). This agent is generally no longer used since most modern dry chemicals are considered compatible with synthetic foams such as AFFF.
MET-L-KYL / PYROKYL is a specialty variation of sodium bicarbonate for fighting pyrophoric liquid fires (ignite on contact with air). In addition to sodium bicarbonate, it also contains silica gel particles. The sodium bicarbonate interrupts the chain reaction of the fuel and the silica soaks up any unburned fuel, preventing contact with air. It is effective on other class B fuels as well. Blue/Red in color.
none of that stuff is good for lungs or electrical parts of any kind. Neither is vinegar, really. You need to vacuum up what you can, blow out the rest, hose down what's left, and you'll still be finding powder in things a month later.
The boat didn't burn down, keep reminding yourself the rest is a lesser problem. Think about getting a less corrosive extinguisher. Kidde makes a special "kitchen" extinguisher that uses plain bicarbonate, and is unrated because it has a wider spread at lower pressure than the UL wants, but it is about the same as other "liter" sized extinguishers and designed to not be corrosive to kitchen appliances, electric ranges, etc.
Then there's CO2 or Halon replacements, with zero cleanup. And foams.
One thing to remember is that when you need an extinguisher, you need it NOW and you will not have time to go looking up which one to use. CO2 is not unreasonable--except for the way it can blow around liquid fuel fires and spread the fuel.
Could be whatever chemical was in your extinguisher, when mixed with acid (vinegar) attacks copper and other metals. You'd have to figure out which one it was to make a better guess.
It might also be a good precaution to change the engine oil & filter, in case any powder got into the engine.