Higher octane for outboards

[boater1234]

I was just wondering how high of an octane a outboard can handle?I know when you buy gas with ethanol the octane rating goes down as it sits so i was going to add an octane booster to the gas.Has anyone done this or does it on a consistent basis when they fill up?

Will a real high octane gas like 98 or 100 octane hurt or help an outboard?

Ok any info would be great thanks guys.

 

[ondarvr]

Re: Higher octane for outboards

Using a higher octane fuel than what's recommended in the manual does nothing but drain your wallet.

 

[Brewman61]

Re: Higher octane for outboards

why you want to go up to 100 Octane?
Pump grade premium would more than suffice, if your motor is designed to run on plain ol 87 regular grade, fill with the 92 stuff.
That should mitigate your worry about octane drop.

To answer one of your questions, the higher octane won't do a thing to help. Octane doesn't = more power or better fuel economy, or anything else.
It merely helps high compression engines run without destroying themselves. That's about all it does.

 

[Silvertip]

Re: Higher octane for outboards

One must be careful about saying higher octane fuel "does nothing" for power. In old, non-ECU, carbed engines that would be an accurate statement. However, two and four stroke engines with ECU's may vary engine timing automatically. Therefore higher octane fuel can indeed allow more spark advance which can provide a bit more power. If the ECU follows a fixed timing curve, then that curve was established for 87 octane fuel (or whatever the manufacturer recommends) so higher octane would do no good in those engines.

 

[Shamus O'toole]

Re: Higher octane for outboards

One must be careful about saying higher octane fuel "does nothing" for power. In old, non-ECU, carbed engines that would be an accurate statement. However, two and four stroke engines with ECU's may vary engine timing automatically. Therefore higher octane fuel can indeed allow more spark advance which can provide a bit more power. If the ECU follows a fixed timing curve, then that curve was established for 87 octane fuel (or whatever the manufacturer recommends) so higher octane would do no good in those engines.

so your saying ECU's can tell what octane your running!?!? or are you saying the ECU can detect detonation and dial back the timing.

 

[boater1234]

Re: Higher octane for outboards

I'm not running anything yet i was just trying to get some input on the whole octane thing.I get non ethanol 90 octane from the marina down by me.

I'm just wondering if a octane booster would make the gas better that is all i'm trying to find out.If not then i won't waste my money on buying it.So if anyone else wants to chime in that would be great.

 

[trendsetter240]

Re: Higher octane for outboards

so your saying ECU's can tell what octane your running!?!? or are you saying the ECU can detect detonation and dial back the timing.

I'm not sure about outboards but the ECU in my car will detect detonation and retard the timing. I am sure that my ECU follows a pre-set timing map. Usually there are two, one for idle speeds and one for high RPM and acceleration.

The ECU follows a timing map while the engine is accelerating. If at any point it detects detonation it will retard the timing untill it stops.

As silvertip mentioned, if the ECU timing map is set for 87 octane fuel then it will never see any benefit from higher octane. However, if the ECU timing map is set for 91 or 93 octane fuel then it will attempt to advance the ignition until it detects detonation or it reaches the timing as set on the map.

Running low octane fuel in an outboard that is set for high octane would result in engine damage if the ECU was unable to detect detonation. All the new outboards I've seen come from the factory with 87 octane fuel requirements. It's possible you could have the timing maps updated by a dealer to allow more advanced ignition timing.

 

[jfadool]

Re: Higher octane for outboards

What do you mean "make gas better?"

In new fresh gas it will increase the octane rating by adding some additives mostly MTBE. Does it increase octane, yes; do you need to increase your octane, no. Most outboards are designed to use 87 octane you don't need better.

Will it make old stale gas better, no; once gas has gone bad the only real use for it is starting a bonfire. You are throwing your money away buy trying to doctor up old gas.

 

[boater1234]

Re: Higher octane for outboards

I guess i see were you are coming from with what do i mean about make it better.
What i mean is will it help the performance of the motor any and will it make the gas last longer?I guess will it do either or just don't waste the money.

 

[ondarvr]

Re: Higher octane for outboards

For a normal outboard its a total waste of money, there is no upside.

 

[Silvertip]

Re: Higher octane for outboards

It WILL empty your wallet quicker. It WON'T increase performance. It DOES NOT make gas better. It DOES NOT increase fuel economy. If that fuel is all you have to choose from, it WON'T hurt to run it but why would you?

 

[109jb]

Re: Higher octane for outboards

If you want to avoid problems with octane loss from the fuel sitting over a period of time, there are basically 4 things that you can do

1. Use a fuel stabilizer. They are made to prevent octane loss.

2. Use a higher octane fuel so that even with a drop in octane the fuel will still have sufficieent octane for the engine

3. Use the fuel fast enough so that octane loss is not a problem

4. If the fuel has been sitting, drain and dispose of it and put fresh fuel in its place.

My family and I have owned outboard boats for many many years and here in the midwest have had ethanol blended fuels for many years also. I have never had a problem. I just use regular 87 octane E-10 and when I put it away for the season I fill the tank and treat the fuel with a fuel stabilizer. Never had any problems whatsoever. I personally use Sea Foam which stabilizes fuel among other things.

 

[5150abf]

Re: Higher octane for outboards

This is one of those wives tales that kills me, you see jounor putting racing gas in moms Oldsmobilethinking it makes it faster, it just doesn't work like that.

There are some larger 4 stroke outboards that require higher ocane but that is just for break in, regular unleaded is all you need.

 

[JB]

Re: Higher octane for outboards

Back in. . . . . um, well, a long time ago when all outboards (except Homelite/Bearcat) were carbed 2 strokes most shops recommended Amoco "white" gas.

"White" was unleaded, about 80 octane, and was mainly used for camping stoves, lanterns, catalytic heaters and outboard engines. In rural areas you could buy it from a pump. Today you can still get it as stove/lantern gas in a can. Low volume makes it expensive, but it is still the "best" gas for small carbed outboards like the JohnnyRude 3s that we love so dearly.

It isn't loss of octane that makes stale 87 bad; it is formation of varnish.

 

[Shamus O'toole]

Re: Higher octane for outboards

This is one of those wives tales that kills me, you see jounor putting racing gas in moms Oldsmobilethinking it makes it faster, it just doesn't work like that.

There are some larger 4 stroke outboards that require higher ocane but that is just for break in, regular unleaded is all you need.

ding ding ding...we have a winner!!!

 

[Frank Acampora]

Re: Higher octane for outboards

Well, JB: The reason for using Amoco White in outboards was because unlike all other brands, it did not have tetra-ethyl lead and would not plug up the exhaust ports with lead deposits after numerous hours of running.

BTW: Tetra-ethyl lead had four ethyl groups attached to it (recognise our friend ethyl?) and that is why it was used: It took less to acheive the result wanted.

That is why "High Test was also known colloquially as "Ethyl." Under heat of combustion, it disassociated releasing the ethyl as, most likely, ethane, increasing the octane. Unfortunately, the lead deposited on valves and pistons, was polluting the environment, and generally creating havoc. It also "poisoned" the platinum catalyst in catalytic converters and the Govt. mandated its phase-out. Probably one of the few good regulations from those years.

 

[JB]

Re: Higher octane for outboards

Exactly, Frank. As I said, UNleaded, though that wasn't my main point.

My main point was that 80 octane was fine for 2 stroke outboards, so loss of octane in stale gas is not an issue; it is formation of varnishes that make stale gas bad.