87 or 93 octane?

[dlandersson]

Does 4 stroke outboard motor performance improve if you increase the octane (rpm, etc.)? My Mercury 50 hp elpt 4S manual just say any gas with at least 87 octane is fine.

[K9Kampers]

On what kinda boat?? (Watch Erik's rigging video)

[WASP18]

According to the "experts", purchasing a higher than recomennded octane is a waste of money. Go to Cartalk.com and search octane in their website.

[Tomfoolery]

Higher octane is needed for higher performance engines that otherwise would suffer detonation or preignition. That's why high octane fuel is associated with high performance engines, but it's not the fuel that makes them high performance. As I recall from thermo classes decades ago, there is actually marginally less energy content in a pound of premium than a pound of regular. And, of course, it costs more.

If it's designed to run on regular, run it on regular.

[Divecoz]

Yep I agree! Its Just A VERY OLD Wives Tale..I would hazard a guess it was propagated by Sunoco.. Remember Sunoco 260? Lots of fellows Back In The Day paid a Very Premium Price for that fuel and put it into very marginal vehicles.. I even tried it in my 427 Cu. In. 1965 Thunderbird at Oswego Drag Raceway? I saw ZERO effect for the extra cost. There are ZERO .. Cheap Options for increasing HP!

Higher octane is needed for higher performance engines that otherwise would suffer detonation or preignition. That's why high octane fuel is associated with high performance engines, but it's not the fuel that makes them high performance. As I recall from thermo classes decades ago, there is actually marginally less energy content in a pound of premium than a pound of regular. And, of course, it costs more.

If it's designed to run on regular, run it on regular.

[dlandersson]

Thank you all very much - just looking at ways to "upgrade" my Mercuty 50 hp elpt 4S w/o replacing it.

Already changed the prop - some improvement there.

Also looking at removing the "restrictor" and well as flashing the ECM.

I am open to suggestions from my more learned peers (which is just about everyone).

Yep I agree! Its Just A VERY OLD Wives Tale..I would hazard a guess it was propagated by Sunoco.. Remember Sunoco 260? Lots of fellows Back In The Day paid a Very Premium Price for that fuel and put it into very marginal vehicles.. I even tried it in my 427 Cu. In. 1965 Thunderbird at Oswego Drag Raceway? I saw ZERO effect for the extra cost. There are ZERO .. Cheap Options for increasing HP!

Higher octane is needed for higher performance engines that otherwise would suffer detonation or preignition. That's why high octane fuel is associated with high performance engines, but it's not the fuel that makes them high performance. As I recall from thermo classes decades ago, there is actually marginally less energy content in a pound of premium than a pound of regular. And, of course, it costs more.

If it's designed to run on regular, run it on regular.

[TAW02]

93 octane in comparison to lower grade octanes burn slower.
123 octane burns slower than 98
260 octane burns slower than 123

so forth. The higher the octane the longer the burn. Some just say a hotter burn, but that isn't really so. Because it burns longer tends to make that assumption true.

The idea that burning 260 octane in an engine will damage it is untrue. Same with 93 vs 87 octane. I burn 93 octane in everything I own including the weed eater. Why?

The higher the octane the better chances it will light the candle a year from now and not turn into a whore's perfume when I forget to use a fuel extender or run the carburetor dry. Gum is a thing with low grade gas. Ethanol is an out an out curse to mankind.

[raycarlson]

higher octane only helps to prevent pre-ignition(knocking) in high compression motors by slowing down to speed of the burn rate.it does absolutly nothing in a compression ratio below 9 to 1, most o/b motors have compression in the 6 or 7 to 1 ratio which lets them run on fuel made anywhere on the planet.it does not burn any hotter or better or last any longer then 87 octane regular.

[Divecoz]

Octane rating is .....all about the amount of compression the fuel will withstand before instantaneous combustion.. That's what makes it" seem" more combustible.. Without more pressure the higher Octane does nothing except ignite like any other grade of gasoline when the spark is added.
Though Octane ratings are very similar in The USA and Canada they can vary widely in other places in the world ..
8to1 compression ratio roughly compresses the fuel and air to 1/8 its original volume detonation takes place with spark / ignition..If that same "size" motor will compress to 12 to 1 you are reducing the volume to 1/12 before ignition thus producing greater force at combustion..
Sunoco 260 was advertising HYPE it was 130 Octane.. 260 TTBOMK was just a Cooler Name..
Ray Does it / 97 or higher octane burn hotter? Well? I am Not sure.. But the force produced is.... greater.. If Its Compressed to a smaller volume..
My Chevy 6.2 ( PP Diesel IMHO) was more powerful when we among other things decked the heads and changed the degree of valve cuts.. we could only do so much and still run Diesel from the pump.. Journals between valves was already a weak point on those POS motors so we welded all mine and re-machined .. but increasing the compression made a HUGE difference in power ... Hahahaha but then you have to remember to strengthen every other part in the whole system $$$$$$$ I warned the kid I sold that truck to.. He didn't listen and tore the 400 Turbo right out of her..

[mastreb]

So I just pulled up to a fuel dock for the first time ever to fill up with non-ethanol gas.

$9.85/gallon. $100 to buy 10.2 gallons of fuel.

That'll be my last tank of that. My motor is specifically compatible with up to 10% ethanol, and I'll be taking that 3:1 discount from now on.

I can't fathom how much it must cost to fill up those gigantic fly-deck stink pots all the time.

[On edit: Looked it up, and it's 10% ethanol max]

[DaveB]

Wham Bam thankyou Mam. In Florida we have laws that prevent Gas gouges and penality is strick.
We also have fuel trucks that deliver to your dock with no ethanol. Price was $ 4.50 octane 89 and min. 50 gals.
You will pay more for less than 50 gals so have a few extra 6 gals to equal that.
Dave

So I just pulled up to a fuel dock for the first time ever to fill up with non-ethanol gas.

$9.85/gallon. $100 to buy 10.2 gallons of fuel.

That'll be my last tank of that. My motor is specifically compatible with up to 15% ethanol, and I'll be taking that 3:1 discount from now on.

I can't fathom how much it must cost to fill up those gigantic fly-deck stink pots all the time.

[Azzarac]

I guess I'll stop complaining now about our local marina's fuel price LOL! I topped off the tank yesterday with ethanol free fuel at $3.99/gal.

[Divecoz]

There were a couple gas stations in Port Charlotte selling Non- Ethanol Gas and IIRC it wasn't all that... much more expensive..

[Boblee]

Well used to think it was a waste but find by using the higher octane rated fuel everything seems to run longer and start easier, we have consistently proved that our Etec and the Honda especially runs much better on the higher rated fuels? we also have a merc 50hp on a poly boat which ran like a dog until I started putting the highest octane fuel in and that is a PIA as it gulps fuel like I have unlimited money to keep filling it.

[Divecoz]

I cannot for the life of me understand why you would see a dramatic difference.. Octane of 87 doesn't have less Explosive power at the same compression as 106 Octane.. The BOOST.. comes from the additional Compression ratio..

Well used to think it was a waste but find by using the higher octane rated fuel everything seems to run longer and start easier, we have consistently proved that our Etec and the Honda especially runs much better on the higher rated fuels? we also have a merc 50hp on a poly boat which ran like a dog until I started putting the highest octane fuel in and that is a PIA as it gulps fuel like I have unlimited money to keep filling it.