Ethanol would be my thought.
It does not have the btu rating as gas so need more to produce the HP

its all about the air to fuel ratios.
I have never tried to run LPG on an outboard but I haave seen it.

on the ethanol.
if your running pure methanol or ethanol it takes roughly TWICE as much fuel to air to make about the same BTU.
the correct A to F ratio for gas is about 14.7 parts air to 1 part fuel.
the roughly correct A to F mix for pure methanol or ethanol is about 7 parts air to 1 part fuel.
so you either have to roughly halve the amount of air OR roughly double the amount of fuel.
easier to double fuel.
depending on the motor not only will the fuel jetting need to be increased but the needle valve may have to have a larger inlet to allow twice the fuel to flow.
its why you can add nitromethane,an oxygen bearing substance,to methanol and not detonate it.
alcohol is given an arbitary octane rating of 100 as you cant compress it hard enough to make it detonate.

on the LPG you have to look up the min and max A to LPG(F) ratios for complete burning.

Several reasons that I can think of.

One, Brazil has no EPA (Environment Protection Agency) to deal with like we in the US do. One person running a motor, even a bit on the rich side, is not a problem. 300 million people doing so is a problem. Brazil probably prefers a motor that will run well. The US does not seem to care about runability. Maybe their thinking is that US citizens will get so disgusted trying to run motors with jets that are too small and they will give up on boating.

Two, ethanol being added to gasoline makes the air/fuel burn a bit leaner than does straight gasoline. Brazil uses a lot of ethanol from what I understand. So, upping the size of the jets to compensate for ethanol seems to be reasonable.

Ethanol needs to be compensated for here in the US but the EPA tries to block folks from doing it. Like installing plugs so that the idle mixture adjustment cannot be easily manipulated.

A number of years ago Yamaha motors intended for sale had larger sized jets installed. Along came the EPA and the jet sizes went down. Also, the anti-tamper plugs showed up.

Take the USA Yamaha F40 carbureted motor for example. It first came out with a #42 idle jet. It ran OK. Sort of. It then went to a #40 jet. Not so good. The F40B has a #38 jet. Terrible. Even with pristine carburetors the motor does not run so well. Install a set of #45 jets and it will start, run and purr like a kitten. Just don't let the EPA know.

The EPA is another reason for the move to EFI motors. They might burn a bit better because of they can change with changes in ambient air pressure and temperatures (certainly at high altitude they will) and are all but impossible for the average person to modify.

I did read that brazil was trying to pass a law requiring any vehicles made or imported to Brazil after 2010 had to run on 100 Ethanol.
it is or was part of their oil independence thing.
biggest difference,other than sheer land mass, that Brazil has over the US is the avalibilty of the raw resources needed to make ethanol.
Brazil doesn't burn there food for stupidity, the US does.

in the US we have parts of maybe 4 states that can get 1 sugar cane crop a year.
Brazil,from what I read, has a few million acres that can produce 3 or more crops per year.

kinda like the soils around the Santa Theresa Distillery in VE.
about all it grows well is sugar cane.

Chavez,in all his wisdom, BANNED sugar cane from being grown in that district and DECREED that only black beans and corn could be planted there.

the farmers SQUEALED, the ag ministery said YEP.
the crops failed miserably just as the local farmers predicted.
happened in Russia in the late forties and china in the early 50's, those man made crop failure famines killed MILLIONS.
enough politics.

I don't know if Brazil has any air quality standards in place, even though ours gets stupid some,or most, times I am thankful we HAVE them.

those of you that don't remember the erie canal burning or that never stayed in los angeles or san diego in the 70's or san fraancisco in the 70's or the dallas/ft worth area in the 80's don't even know what SMOG is.

just think what our air and water quality would be if we had NO restrictions on ANYTHING.

I moved to Burbank, California in the late 1970's. Got there in early summer. The air would burn your eyes. I was there for several months and one day the air cleared. There were nearby mountains that I had never seen and did not know they were there.

The biggest source of pollution is too many people. What is the EPA doing about the too many people problem? Nothing it seems.

how you figure it was to many people?
they wernt farting that much when I was there.\
there were A LOT of cars and some smokey powerplants if that's what you mean.
so they had 2 choices.
1 restrict car ownership,that would go over well.
or 2, place strict tailpipe emissions standards on cars.
could you imagine the wailing if the restriction was 1 vehicle per address??????
you just think the right wing wails now.

they wail like crazy now over some of the emissions standards for gasoline and coal fired plants.
however having lived near a coal fired plant years ago and dealing with the acrid acidic smells and the coal dust settling on everything, I am happy they now have standards.