10% ethanol fuel vs ethanol free fuel for boat/outboard motor use?

Joined
Dec 11, 2020
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In previous years i always ran what we in europe call E0 fuel which is octane 98 gasoline with 0% ethanol, this because i know that this is easier on the fuel lines/gaskets and does not attract moist or leave behind residue as much as E10 which is the regular octane 95 with the legal requirement of 10% ethanol for emissions(scam).

However with the recent rise in fuel prices and even normal E10 fuel rising above 2 euros a litre i decided to now switch to the cheaper E10, this because it was more like peace of mind to run the simple carburated 2008 Honda hp 20 4 stroke outboard 380cc 2 cylinder on the fuel more or less designed for modern turbo cars with the higher octane rating, in theory this motor as a normaly aspirated motor should benefit from a lower octane fuel.

My only concerns are:
- Because ethanol is hydroscopic the fuel absorbs moisture from the air, all modern cars have vacuum sealed fuel system/tank so that is not a problem. However my boat just has a oem plastic 25l tank with a vent screw on the cap. The tank is in outside air/rain etc.. and is not covered. i can not close the valve because i tried this before but if the sun kicks in it almost explodes because of the pressure build up:ROFLMAO:

- My honda owners manual says that the system is designed to run max 10% ethanol fuel, i use the boat a lot and eventhough it doesnt consume a lot its more or less empty every month so i dont see the deteriorating of the ethanol as hazard like it is with a lot of classic vehicles.

-Outboard motors run at lower water/oil temps and eventhough my engine sees a lot of hours at full throttle 25 knts the nr1 problem with (carburated) outboards is fuel diluition at (cold)trawling speeds which is invitable. Last year my oil also came out pitch black like it came out of a 15k oci diesel engine oil change and smelt like gasoline.
Will the ethanol/fuel in the oil be a reason for problems because the motor spends its life in such a humid enviroment? I mean problems that can be created by the ethanol.

Let me know if you have any experience on this topic and if theres something i am missing out on.

-Powerwise do you think there will be any (marginal) difference? This is not a 2.5 bar boost world rally car but a carburated 380cc 2 cyl 4 stroke with 20hp. Generaly speaking the lower the octane the more power it would have. It has no knock sensors so everything is fixed.
Don't dare leave E10 in there over the winter.
 
Joined
Jul 16, 2005
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Montague, NJ
I always run E0 in my toys and boats in the last tank of gas or in anticipation of the last tank along with marine stabilizers.
Zero issues in my OPE using stabilized E0 exclusively in them and my fuel cans also.
I have no love for fuel system cleaning anymore, so a little more fuel cost outweighs and prevents aggravation.
 

FZ1

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I always run E0 in my toys and boats in the last tank of gas or in anticipation of the last tank along with marine stabilizers.
Zero issues in my OPE using stabilized E0 exclusively in them and my fuel cans also.
I have no love for fuel system cleaning anymore, so a little more fuel cost outweighs and prevents aggravation.
E 10 Chevron with Techron, stabil,and a dash of Ring Free runs great in my 2 stroke. Very hard to find E0 down here.
 
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Jul 12, 2012
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Caldwell Idaho
All I can tell you is 90% of my business is cleaning and repairing boat injectors for marinas, E10 is responsible for a lot of injector and composite fuel tank damage, I see it every day.
Unlike car engines boats live on water, the fuel gets saturated with absorbed moisture and at some point it will drop out. The moisture gets into the injectors and corrodes them. I am doing a set today that have rust inside the injector from a metal fuel rail
Would that depend on the boats usage? It seems most recreational boats sit more than they are used.
 
Joined
Dec 5, 2003
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New England, USA
From my other thread on ethanol fuel damage to a low usage car that sits for extended periods;
f carb deposit 17.jpg


Avoid alcohol blend fuels if possible. That said, and I'm just learning ocean boating and the marina environment, our marina's fuel is supposedly 'treated' by the supplier to moderate ethanol issues and I don't hear of as many issues there as with the lake boat (fueled from a can) crowd. Do your homework on your fuel supplies and use a reputable additive if necessary.

Here is our marina's fuel provider for reference; Valvtect Marine Fuel
 

FZ1

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Feb 7, 2008
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Texas
If there is one near you, QuikTrip has E0. They have been building new ones in Texas like crazy in the last few years.
Thanks. I think the E0 is a county by county thing in North Texas. Motor runs fine for 20 years on E10.
 
Joined
May 7, 2004
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Thanks. I think the E0 is a county by county thing in North Texas. Motor runs fine for 20 years on E10.

You won't find E0 for sale in places where the EPA requires gasoline to be oxygenated, and I believe there are some places in Texas where that is the case.
 
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Joined
Jun 2, 2009
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I did not know about this and ran cheap ethanol gas in our boat the last two years. Now it's sitting with some type of fuel problem. And I used Marine Stabil as well.

Don't know if it was the fuel but it will be E0 from here on out.
Hopefully just some dirty carb jets.

Always E0 91 octane in marine use or anything with a carburetor.

I have a 90 hp 1985 Johnson 2 stroke. The manual doesn't even say anything about ethanol because it wasn't around then (requires 86 octane minimum). It has seen 91 octane E0 its whole life. Had to rebuild the carbs a couple years ago due to trouble with warm starting. After 35 years the carbs were clean as could be, the needles were just worn. I put Seafoam marine, Startron, and Techron marine in the gas tank (and oil, the VRO system broke a decade ago and not worth fixing) and never have fuel or storage problems. My other small engines get Seafoam and Startron and never a fuel problem.
 
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