What is the best fuel to run

[Pat Delaney]

1B766657 2010 Pro XS
87 octane ethanol or 90 octane ethanol free?

[Savage]

87 is fine for your motor.

[4motion]

But isn't ethanol gas going to cause the inner lining to break apart? When I bought my boat and looked inside the VST fuel filter housing there were some golden debris (hose lining breakdown) and small pieces of grey rubber from the hose inside of the fuel filter housing. The seller told me he just used 93 octane (and 93 has ethanol). From there on, I only used 91 non-ethanol because there were no 87 non-ethanol here in WI. Almost three years now and I just checked my VST fuel filter housing yesterday and didnt see any debris inside.

However, per Merc Manual it says use 87 minimum. So use 87 with ethanol anyways?

[Squire]

I have a 2017 2 stroke optimax and I was running the Marina 90 octane ethanol free and it
clogged up the motor and I had to run the Mercury clean thru it. I went back to
a gas station that is 10% Ethanol and is "Top Tier" and motor has been running great.
87 octane runs HOTTER than 90 octane. Higher octanes run cooler to prevent pre-detonation
with higher compression engines. The fuel lines and stuff by Mercury have been switched over
for quite a while now to handle ethanol gas. If you look up on the Mercury site
about Ethanol gas, 10% was actually good for the motor, helped it stay clean.

So that is my experience and research.....

[Bryanmc57]

87 octane is the recommended fuel for your motor. Burning higher octane fuel which burns cooler can lead to carbon issues. If you found pieces of fuel line in the filter chamber, you should change your primer bulb and fuel line all the way from the tank to the pulse pump with ethanol safe fuel line.

[angle iron]

https://www.bbcboards.net/showthread.php?t=22490

[EuropeanAM]

See the FAQ Section Post:
Oil, Battery, Spark Plugs, Fuel and Fuel Additive Recommendations

[SilverFox579]

But isn't ethanol gas going to cause the inner lining to break apart?

No. If that were true I'd have replaced lots of fuel system parts years ago.

Fact is, my Optimax still has the original pulse pump and black fuel line stub it left the factory with after 15yrs of 87 E10 from a top tier station always with the cocktail as recommended in the link Don provided above.

[Champ2005]

For my engine the minimum Don states is 87, so if I run 90+ will it build less carbon?

[Savage]

For my engine the minimum Don states is 87, so if I run 90+ will it build less carbon?

No

[SilverFox579]

For my engine the minimum Don states is 87, so if I run 90+ will it build less carbon?

As Savage said - no.

Your engine won't benefit from higher octane. Problem is the how the statement is worded...minimum in this instance does not mean higher is better, it means no less than 87.

[Savage]

If you want less carbon, run WOT more often. These motors are designed to be running MAX RPM's, not putting around

[EuropeanAM]

As Savage said - no.

Your engine won't benefit from higher octane. Problem is the how the statement is worded...minimum in this instance does not mean higher is better, it means no less than 87.

+1

These engines run their DIRTIEST at IDLE and at WOT.

If you want a clean engine... run it where it gets it's best fuel economy (3800-5100 RPM range) for a nice long run during each outing (preferably end you outing that way).

[Pat Delaney]

Thanks Don, Savage and BBC. Nearby Murphy station started carry non Ethanol fuel and thought I'd ask. I knew I read it somewhere on FAQ Don, just couldn't recall (that age thing).

PD

[hooken203]

This is a great discussion. I think that if you run Dons recommend cocktail all the time you will have to worry less about what fuel you run. I have ran 91 and higher octane in all of my outboards since 1987. Mostly to avoid the ethanol. I worked in a GM dealership in the day where ethanol was causing a bunch of problems. All manufacturers have improved their product to better tolerate E10.

[4motion]

No. If that were true I'd have replaced lots of fuel system parts years ago.

Fact is, my Optimax still has the original pulse pump and black fuel line stub it left the factory with after 15yrs of 87 E10 from a top tier station always with the cocktail as recommended in the link Don provided above.

Then what is this? Was this not caused by ethanol over time? I am curious.

[JustinNC]

This question got me thinking as well. I've got a relatively high traffic BP station near me. It's super convenient for 95% of the fishing I do. Instinctively I run 89 non-ethanol, but this thread has me rethinking, especially at $0.60-$0.80 difference/gallon and 48 gallons of fuel (though I try not to let it get that low)

[EuropeanAM]

Then what is this? Was this not caused by ethanol over time? I am curious.

No doubt that is indicative of ethanol degredation. This is why fuel lines need to be inspected regularly, and in many cases, replaced in the 5-6 year range to prevent problems.

Earlier versions of that line didn't stand up to 10% ethanol. Later versions (with blue or black print) DO. We often find that fuel samples (today... not 10 years ago) in a case like this are SIGNIFICANTLY higher than 10% ethanol. One case last season I say 27% from a local green and white w/yellow brand station.

It's also important for that line to be heated at the end when installing. Simply dip the end in piping hot water for 20-30 seconds, shake the water off, and slide it onto the barb or nipple. Failure to do this will often grab the inner liner, tearing it loose and folding or bunching it up. Usually creates a heck of a fuel restriction... if not it starts accelerated failure of the inner liner due to delamination.

[JustinNC]

One case last season I say 27% from a local green and white w/yellow brand station.

Pure ignorance, but who tests it? Assuming the station had the generic "May contain up to 10% ethanol..." stickers as well?

[EuropeanAM]

The guy that has to deal with the aftermath, usually...

And the sad part is it's not the station's fault. Blending error going into the truck, more than likely.