put 87 octane car gas into F150LA (SHO version)

[kylakerider]

I have a new-to-me 2015 Yamaha 150 SHO (F150LA I think). Out of habit from my older engines, I filled up the tank with regular car gas, 87 octane, 10% ethanol. Never had a problem with that on older engines.
Now, yikes, I read the manual for the 2015 150 SHO and they are pretty emphatic that it needs at least 89 octane. I understand the engine knock thing, and the timing retarding to prevent knock, been there done that on car motors for years.

But what to do with this one tank of 87 octane this time? Should I just ignore it? If I hear any knock I can change speed or not accelerate fast perhaps. Or maybe put in some store bought octane booster just for this tank? Any thoughts appreciated.

ps: I'll go to 89 octane car gas (10% ethanol is allowed per Yamaha manual) for future fills of course)

thanks
Paul

[boscoe99]

I would just not slam the throttle down when getting onto plane or run the motor at wide open throttle, just to be on the safe side. Maybe once you are down to half a tank, top off the tank with gasoline rated at 91 or 89 octane.

Your motor has a knock sensor which hopefully will protect it should knock (detonation) occur.

Good for you for having read your manual. All too many don't.

[kylakerider]

I was thinking something similar, thanks.

What do y'all think of a one time use of an octane booster?

[99yam40]

How big of a tank is on this boat?

You could transfer some of it back out and into your regular auto or truck if they will take e10 87.
most trailered boats are not hard to get fuel back out, ones that sit in water can be a pain.

need to look at labels to see what is used to boost octane before deciding to use them.

running e 10 is not a problem if you do not let the fuel stay in the tank for months at a time.
most people do not use most of the fuel in their tanks in a months time so some of it will be around for many months.

remember the vented tank will allow moist air in and the E will suck it into the fuel.
any water in a tank will ruin/kill the fuel

[kylakerider]

tank is 38 gallons and I just topped it off this morning. The good news is that I'll be using it a lot over the next couple of days, probably well below half by Wed/Thurs. I could siphon out some, would have to pull the boat out of course. good thought.

I did find on the internet that MMT(Methylcyclopentadienyl manganese tricarbonyl) is the octane booster used by gas refineries. If I can find an octane booster with that this should help some. I also read that most octane boosters really only boost by 0.5-1.5 points at the most. If I can get with that additive and a boost of 1 for this gas tank full should be fine.

Yea on the ethanol in gas ruining the gas. Over my 60+ years I've had experience with dozens of engines, many of which were kept with gas in the tank all winter, sometimes for 2, 3 and more years. Never had a problem....till a few years ago not too long after E10 gas came out. My jetski recently had my first ever "bad gas" in the tank problem. And I see the the marinas are now selling E0 gas lately, surely for that reason. Good point 99yam40.

ps: my father always said "hey, some ethanol in the gas is good, it will absorb the moisture and not ruin the gas". Seems like that is not correct. Thus the E0 gas being sold and used widely lately.

[99yam40]

with E10 they use the e to boost the octane.
So when it sucks up water and drops out the remaining fuel is very low on octane

[kylakerider]

Good point too. I actually didn't know that. Wow, that means that I've probably been running with less than 87 at some times.

Hum, that seems to imply that the engine can run (without knock/detonation) with 87 or some less. I think what I'll do this time since the current gas is "fresh", is to just run it as-is and as the tank runs down dump in some cans of 89. I'll just take it easy on the throttle until 2 or 3 such 5 gallon cans are dumped in. Should be just fine after that.

Ps: I did read that the better additives that contain MMT are rather nasty in that they stain everything they touch and even have a slight hue to the exhaust (not sure if that is of any consequence at all).

Thanks to all for your thoughts.

[TownsendsFJR1300]

If you can (after this tank), run NON-Ethanol fuel, It's WELL WORTH the extra $.

The engine may be able to handle it but as posted above, Ethanol sucks moisture / WATER out of the air and into your fuel tank-which is NOT good.

That (WATER), eventually makes it into your engine...

[kylakerider]

I just checked at the local marina. They have 87 E0 and 89 E10. Seems kind of odd that they don't have 89 E0.

My current plan is to run 89 E10 (car gas) this summer, then at the end of the season either have the tank empty, or put in some 87 E0 if there is left over car gas in the tank. Then in the spring fill it up with 89 E10 and go through the summer. That avoids it sitting all winter with E10 and still gives is 89 E10 for the summer.

I also ran it yesterday with the 87 E10 car gas. Stayed below WOT and no hot rodding. No evidence of knock/detonation. Waiting till I can get a couple of cans of 89 E10 in it, probably tomorrow.

Thanks again for all of the advice.

Hum, gas is more complicated that I knew, good stuff.

[kylakerider]

Oh, one other thought: As I'm now understanding that the E10 is used to raise octane in otherwise sub-87 gas, seems that running left over 87 E10 car gas in the spring likely has some water in it leaving the resultant mixture sub-87. It ran fine this spring with a half a tank of that mix, so....the engine's EFI timing adjustment must be enough to handle this. Thus fresh 87 E10 should not be a problem. But as stated above I'll go to 89 E10 as Yamaha recommends as soon as practical.

[fairdeal]

As I'm now understanding that the E10 is used to raise octane in otherwise sub-87 gas, seems that running left over 87 E10 car gas in the spring likely has some water in it leaving the resultant mixture sub-87.

The potential issue with "gasohol" is not that "some" water in it "lowers the octane"
The problem arises when a considerable amount of water mixes with it;

once the water content exceeds about 1/2 of one percent -
"phase separation" occurs.

that means that ALL of the ethanol, and the water, separate from the gasoline,
and sink to the bottom. (where the tank pickup is).

The engine will not run on that, and the water will corrode the fuel system parts.

The gasoline floating on top now has 2-3 points lower octane than the E-10 did.

[pstephens46]

In NC on vacation. They have 93 non ethanol for 3.29/gallon. That would be the stuff.

[kylakerider]

That's for sure. That's also a bargain. My local marina (who claims to have the lowest gas price in KY lake) has 89 E10 for $4.29. Their 87 E0 is $3.49. The later is over $1 above street price for 87 E10.

I'm going to start looking at street gas stations to see if any of them are competing with the marinas on gas in any way. But heck, if NC weren't so far away it would almost make sense for me to pull the boat there for a fill up

[99yam40]

if their EO is 3.49, why are you not filling with that instead of the E 10 at 4.29

[boscoe99]

if their EO is 3.49, why are you not filling with that instead of the E 10 at 4.29

Octane is too low.