higher Octane vs no ethanol

[harvey5560]

Hello,

I have read lots of threads regarding higher octane fuel being a waste of money with no real benefit for my 2006 Yamaha 50 HP two stroke but what about if the 91 Octane fuel was ethanol free?

I live in Ontario Canada and only one major brand of gasoline does not put ethanol in all its grades. Shell gas has 10% ethanol in 87 octane, 5% in mid range 89 and 0% in premium 91 octane.

The owners manual for my outboard says 87 octane or higher. My question is, Will the 91 octane fuel hurt my outboard at all??/ and is it worth it to avoid ethanol problems?

thanks

[wncmtns1]

Why not just use Stabil marine formula (blue, not red). Supposed to be formulated just for that purpose. I use it in all my small gas engines to deal with ethanol.

[99yam40]

The higher the octane the slower it burns, It is not that much higher , but I have no idea if will hurt the motor or how it would hurt it

[harvey5560]

Thank you for the responses. I know Stabil is a great product and have used the "Red" formula in my other small engines but Im not talking about treating the ethanol problem im talking about not introdcing the problem in the first place. The cost to use the 91 octane fuel is not overly expensive so my only concern is damage to the outboard.

If anybody else has some insight on this question I would appreciate it.

thanks

[Tucker]

Premium fuel will not hurt your motor. The manual says 87 or higher right? I think you're only going to be able to dodge the ethonal bullet so long though.

[awaikart]

Minimum required octane for all yamaha outboards (except F250 and F350 89 octane) is 86 octane. Being that most fuel stations only carry 87 octane that is the closest you can get. Running high octane fuels in an engine designed for low octane fuel can result in incomplete combustion causing excessive carbon and a waste of money. Detonation (engine knock) can occur with excessive carbon build-up which over a period of time will eventually lead to pre-ingnition and engine failure. So bottom line is do NOT run the higher octane fuel in your yamha outboard motor.

[CK Egret]

I asked Yamaha the same question. In my case the only non ethanol gas in my town was 93 octane. They told me that the benefit of running non ethanol 93 octane gas outweighs the problems of running ethanol fuel. The previous poster is correct, higher octane gas can cause a build up of carbon but this can be addressed with running ring free to prevent carbon build up or seafoam to remove it.

In a perfect world we could all find 87 octane non ethanol fuel but in the meantime I will continue to run the lowest octane non ethanol fuel in my boat. I currently run 90 octane non ethanol fuel in my 2002 200 HPDI.

I asked this question on Yamaha's facebook page but cannot search for it. If you are willing to look though there response is on the facebook page.

[rodbolt17]

given a choice between E crappola and straight up gasoline at 91-93?
Ill take the 91-93 octane, run it for 20 minutes or so each outing above 5000 RPM and decarb it every 100 hours and let it ride.

[Tucker]

How much is 93 in Canada? Just check my marina and it's at $3.60 for 87!

[rodbolt17]

our marina sells only 89 octane at 3.50 a gallon AND the great state of NC no longer requires ethanol content to be posted, the law was allowed to expire july 2010.
cant wait for the first doses of the great E 15 SHEETOLA.

[harvey5560]

In Canada we sell the fuel by the litre. One gallon is approx 3.78 litres.

Our 87 octane fuel right now is $1.12 a litre ( $4.24 per gallon). The 91 Octane fuel with NO ethonal is around $1.25 a litre ( $4.73 a gallon).

[Toulla]

High Octane vs ethanol

Rodbolt, I am with you!!! Yet I can't help but wonder, why is my little 2001 F 25 all of sudden sounds like it got loooose valves? I checked them and are with in specs. The only variable; Rec fuel 93 octane; used to run Chevron mid-grade 89 octane with up to 10% ethanol and ring free along with stabill and a fuel water separator. No problems for 12 years. Dropped the boat in Florida, filled up with 93 octane rec gas and the motor is pinging. No carbon build up. Pulled the plugs, the piston tops are clean!( Run Ring Free since new) did a shock treatment at 300 hrs. Now at 560 hours. I am suspecting the 93 octane fuel does not seat well with this Yam-Merc motor. I will transport Shell Mid-grade 10% ethanol fuel for my next fill up; cant find Chevron in South West Florida or any tier one gas at any Marina for that matter and see if the tapping, pinging, knocking and VERY, VERY! annoying noise goes away. If it does I am back to 89 octane 10 % ethanol fuel, with all its culprits! I want my sweet Yam- Merc motor Back!!!