Make and Make Do
Last time we talked about some modifications we could
make on old two-stroke outboards to clean them up.
Now let’s look at making those modifications
even more effective with a cleaner fuel.
Ethanol is that fuel. Since it is infinitely soluble
in water – that is, soluble at any ratio –
a small amount of fuel would dissipate relatively
harmlessly rather than collect on the surface and
choke off the oxygen exchange that aquatic life needs.
Ethanol offers other advantages like being 100% made
in the USA, being an oxidizing fuel, and reducing
combustion chamber temperatures. The latter is why
race engines burn alcohol, even though they use (toxic)
But how do we get two-stroke oil to dissolve in ethanol?
It won’t. At least cheap petroleum oil won’t
do it. But expensive synthetic oil will.
So let’s talk about what synthetic 2-stroke
oil is. Don’t be confused by labeling. Some
of the stuff they call “synthetic” is
really just highly modified petroleum oil. This is
not the same thing. We are talking about fully synthetic
“Ester” should be a clue to those who
know a little chemistry. These “fully synthetic”
oils are esters of vegetable oils. In a word, biodiesel!
For simplicity and comparability, though, I conducted
these experiments with AMSOIL Saber Outboard, an ester-based
synthetic ester oil. At around $8 per quart it is
rather expensive, but it comes out comparable or cheaper
than petroleum oil when you consider that you only
need half as much. I also think they add something
to this oil to help it cling to the moving parts better,
so maybe it’s worth the money anyway. (Note:
don’t confuse this with AMSOIL Saber Professional,
which is not rated for marine use. It matters.)
In case you were wondering, I’m in no way connected
to the AMSOIL people. I only went with this product
because a casual internet search led me to believe
they’ve done the most work on applying synthetic
technology to outboard oil. And being a major name
in racing oil, it should be easy to find a dealer
wherever you are. But I’m pretty sure any synthetic
ester oil that’s meant for outboards would be
I should note that AMSOIL only officially recommends
this oil for use in gasoline of no more than 10% ethanol.
Apparently this is because it can separate into layers
if left sitting still for a long time. The solution
is simple – shake the tank before use. If you
are towing the boat to the water, this is highly unlikely
to be a problem. Keep your fuel free of water –
water makes it much harder to keep the oil from separating.
I recommend venting the tank periodically, rather
than leaving the vent open. Less chance for water
to get in.
So how much ester oil should we use? AMSOIL Saber
Outboard recommends 100:1 on the label. This is for
newer engines that are made for 50:1, and these old
outboards require about double that. Since the idea
is that you need half as much, I use half of what
OMC recommended with regular outboard oil. In 1955,
they said 24:1, so I started with 48:1. I suppose
there is some leeway here, since the factory ratio
is meant for 30w automotive oil. Even mineral-based
modern 2-stroke oils are much better than 30w auto
But there’s a wrinkle. There is some question
as to the relative lubricity of gasoline and ethanol.
There is little research and even less agreement as
to whether gasoline or ethanol has better lubricity.
One would think that gasoline has some lubricity and
ethanol almost none. But some of the limited research
has found that ethanol “blends” (which
might be E-10) better lubricity in two-stroke engines.
The bottom line is that we have to trust our own
observations over anything we read from someone who
might have an agenda. 48:1 actually seemed to work
fine, but I was concerned as to whether it would stay
OK in storage. Ethanol is a good solvent and might
wash the oil out of the bearings. At 48:1 the motor
felt a little tight after sitting for a week, so I
switched to 40:1. It seems a little better now, but
I still feel like I need to use fogging oil if I’m
storing it more than a week. This might be paranoia,
but in the absence of reliable data, paranoia is not
all bad. I’d rather use fogging oil than increase
the oil in the gas any further, because at least the
fogging oil burns off and then it’s done with.
The oil in the gas is always there, so we should keep
it to the practical minimum.
At 40:1 we still get a cloud of smoke, but now it’s
white and doesn’t smell nearly as acrid as the
blue petroleum cloud. But you can also get fooled
by the new smell. The ester oil burns with an aroma
reminiscent of hot metal. Don’t panic. Feel
your waste cooling water to determine whether you’re
truly running hot.
“So, what, do you brew this stuff?” You
could, but it’s a pain in the butt and in the
USA it requires a license from the Bureau of Alcohol
Tobacco and Firearms. I wouldn’t bother.
Fortunately, many urban areas have a gas station
that carries E-85. This is simply 85% anhydrous (no
water) ethanol and 15% gasoline. Apparently a number
of cars made since 2000 were designed with the ability
to burn E-85 just as easily as gasoline. E-85 costs
about the same as regular gasoline (this might change
as petroleum gets scarcer) and reduces hydrocarbon
emissions about 85%. The latter is of course completely
predictable, since E-85 contains 85% less hydrocarbon
than gasoline. The government
will help you find sources at.
Work on the engine
First and foremost, check your compression. This
isn’t going to work in a motor with marginal
compression. It should be about 80 to about 100 psi.
If it’s low, a new head gasket might fix it.
But don’t do this unless you have to and take
all precautions against breaking off the bolts in
the casting! It’s easy to do and hard to fix.
You may have read articles about ethanol in cars,
which can require some relatively extensive modifications.
In particular, the carburetor’s jets need to
be bigger. (If you have injection you need a kit for
around $600.) Here we have it very easy with simple
old engines. We don’t have fixed jets, so we
just open the mixture screws a bit when running alcohol.
Isn’t low-tech great?
But you should consider rebuilding that old engine’s
fuel system if you haven’t already. Natural
rubber gaskets from the old days can’t tolerate
alcohols, but modern synthetic rubber can. Besides,
it’s cheap and we’re only talking about
3 hours or so. Max’s articles or his book (Cheap
Outboards) can guide you there.
One final thing to consider is your fuel tank. Steel
tanks tend to rust faster with ethanol. I’d
get a cheap plastic tank, which will last about forever
with any fuel if you keep it out of sunlight. If you
have a pressure tank engine, this might be a good
time to convert it to a fuel pump. Again, Max’s
book is the best resource out there.
At the same time as upgrading fuel system parts,
you might also replace the rubber oil line on the
side of the crankcase. If it’s original –
and it probably is – it won’t handle ethanol
Ethanol is less flammable volatile that gasoline
and needs a blue-hot spark to ignite. This demands
the ignition be in top condition. Anything less than
a bright blue SNAP won’t cut it. If you have
trouble with igniting the ethanol, consider hotter
spark plugs. But first try brand new fresh plugs of
normal specs and check the points for condition and
gap. And remember that with a magneto ignition, cranking
faster makes a hotter spark.
In the articles on automotive ethanol conversions,
they recommend advancing the spark a bit. I didn’t
find that to be necessary in this case.
Seals are one thing that worries me here. I didn’t
bother to replace any of the seals in the engine,
and I don’t know what they’re made of.
If they are not alcohol-resistant, they will eventually
fail and I will have to rebuild the powerhead. Here
I am mostly talking about the crankcase shaft seals,
and replacing them involves pretty close to a full
rebuild. On the other hand, this is probably not terribly
difficult on a motor with so few moving parts. (Famous
Since ethanol is less volatile than gasoline, it
needs more heat to vaporize. Cold starting might be
a challenge in cold weather. The simple way around
this is to carry a small bottle of gasoline/oil mix
and squirt some in the air intake if you need to.
Fortunately, using E-85 it seems fine without a primer
in any weather nice enough for me to be boating. I
suppose the gasoline parts vaporize fast enough to
get it going.
How to run the engine on Ethanol
There are not many differences, but let’s run
through the process as if this is the first time we’re
• Fill the tank with E-85/synthetic oil 40:1
mix – 3.2 oz per gallon. Or do it the smart
way. A gallon is 3,785.4 mL. So 96.6 mL of oil per
gallon of E-85. Use a syringe if you haven’t
made a calibrated measure.
• Shake well before use.
• Back out the high-speed mixture screw about
¼ turn from where it works well with gasoline.
You’ll refine this as you run it.
• Prime the fuel line as normal.
• Turn up the throttle to the “start”
range, choke like normal, and pull the struggle
string. When you pull it, gently engage the pawls,
then pull the cord briskly. Too slow and the spark
won’t be hot enough. It should fire in three
pulls or less, just like with gasoline. Don’t
bother to go past 6 pulls.
• If it doesn’t start, try a squirt
of gasoline mixture in the air intake.
• If it doesn’t start in three pulls
after that, something else is wrong.
• Once it’s running, open the choke.
I find I have to baby the choke a little longer
than with gasoline – just a couple seconds.
Then I have to turn the throttle up a little higher
than with gasoline to keep it running. After less
than a minute of warm-up, I can use any rpm.
• Adjust the high-speed mixture when you’re
up and running, then the low speed mixture when
you have it warmed up and return to idle. (Just
like that worn-off print on the cowling says.)
That’s all there is to it.
Less smoke – At least nicer smoke. Not the
acrid, choking smoke I used to have.
Less plug fouling – surely a function of less
No carbon fouling – It might be my imagination,
but this stuff seems to have removed some carbon fouling
from the engine. Maybe I can get rich selling ethanol
as an engine cleaner.
Less water pollution – The usually oily sheen
at idle is barely perceptible. And the oil that is
present is biodiesel, which is more biodegradable.
Ethanol itself is also relatively biodegradable in
water, and it forms no oxygen-blocking film because
it dissolves in water and dissipates rapidly. Check
out samples of the water from identical barrel-testing
Here’s the gasoline mix
And the E-85 mix. One part of the bucket got oilier,
so I show the oily spot and the less oily part in
These water samples came from running starting up
the motor in a new 5 gallon plastic bucket filled
almost to the top, idling 5 minutes, running 10 minutes
in gear at halfway between “start” and
“fast”, then shutting down and immediately
photographing the sample. The visible difference is
readily apparent. It smells like a weak martini with
ultra-cheap vodka, which is a distinct step up from
the stomach-turning aroma of the former “petro-mayonnaise”.
Now this is not 100% fair, since in the above results
the ethanol has the advantage of the crankcase bleeder
bypass. Let’s level the playing field. This
is how much waste fuel the bleeder collected during
the test run.
And here’s the bucket with the bleeder waste
This isn’t exactly laboratory water testing,
but the results speak for themselves, I’d say.
Especially since ethanol and ester oil are more readily
biodegradable than their petroleum counterparts.
There’s more to this than simply reducing emissions
of some “obsolete” outboards. In fact
these motors are no longer “obsolete”
if their emissions are brought in line with modern
expectations. Not only does this allow poor people
like me to be more environmentally conscious, but
it also reduces the need for new motors. It takes
a tremendous amount of energy to refine, cast, machine
and assemble that aluminum into a motor. So getting
more use out of the motors we have means less energy
used, less oil drilled, and less greenhouse gas for
the same end use served.
Even better, our new power source is not based (predominantly)
on petroleum, whose carbon has been locked up for
millions of years. It’s based on corn and soy
that were grown last year. This means very little
net disturbance to the carbon cycle. You can almost
view it as liquid solar energy. The only way to go
boating with less impact is to row or sail.
Finally, nobody’s kids or parents have to go
off to the Middle East to get shot at to secure access
to Ethanol or soy oil. They come from farmers right
here in the USA who desperately need the market. Why
should tax dollars pay our farmers not to grow crops
when we could be using these folks’ skills to
grow our own energy? Growing our own fuel paves the
way for real economic stability and national security.
This is true even if you think there’s a lot
of oil left, and it lets us save that oil for purposes
where there is no currently viable alternative. I’d
rather make that oil into epoxy than burn it. (Until
they come up with soy epoxy, anyway…)
In that light, I hope this work is a small step toward
a much greater goal. Either way, it sure makes me
feel better about running that old outboard.
Madison, Wisconsin, USA
A version of this article with fewer
photos but further discussion can be found in the
October 15, 2006 Issue (Vol 24 - #11) of Messing
About In Boats.
Other Articles by Rob Rohde-Szudy: